Exchange is always great (massively enjoy it myself) - and extremely important if we want to move forward as singers and teachers. This includes, for me personally, to be sceptic about everything: One method that gets everything right doesn't exist, just methods that work better for individuals, and we need to choose the one that works best for us individually.
It's important though that we don't take things out of context and interpret them in a way that wasn't implied, so I'd prefer if we really kept to what the other one actually said, instead of interpreting it freely and reading into it what we want to read:
I nowhere said that SLS teaches to belt. What I actually said was that if you want to belt, SLS is not right for you, and that shows its limitations. What I also said is that students who are SLS trained and still wish to create a belt-like sound (there is no such thing as "one Belt" - it means very different thing to different people and singing methods) will run into problems. I also said that's not SLS's fault, but again: it shows its limitations.
It is completely okay if you personally don't want/need to belt and don't feel it is necessary for you, or not required for the type of music you sing.
There are lots of people though who DO want to belt (and indeed need to for professional reasons), and it is important that we, as singing teachers, respect these wishes. A technique that doesn't enable the singer to sing healthily in ANY style is not a complete technique. It is not up to us as teachers to decide for the student what and how they can, cannot, should or shouldn't sing. We are there to enable them to sing healthily in ANY style and vocal set-up they want to, without being judgemental. Or to be honest enough to send them to another teacher if we can't teach them what they want to learn. That's the only reason why I bang on about Belting in this context, not because it is the most important thing in the world to me.
SLS alone e.g. won't cut it if someone requires a Broadway Belt. I can say this with 100% certainty, because I worked in Musical Theatre for many years. SLS works on the very principle that we thin the vocal folds as we ascend through our range. This is very close to the way we teach classical singing, and completely fine. If you sing like that in Musical Theatre though, you will be very limited with regards to the roles you will be able to play. Personal choice.
What I personally don't deem right, is that we, as teachers, try to convince a student that there is only one way to sing, and that e.g. "Belting is unhealthy". You can have a personal opinion that you don't like or don't need it, but you can't say it's not an option. However, Seth himself says that Belting is unhealthy and dangerous because of using excessive airflow and tension - that is his personal opinion about what Belting supposedly is, and I would certainly agree that a long closed phase coupled with too much airflow is potentially damaging.
Everyone who ever learned to belt properly however knows that exactly the opposite is the case - healthy Belt requires extremely little airflow, because the subglottic pressure is very high to start with, due to the long closed phase of the folds. So instead of telling people that Belting is unsound (which is a judgement, not a fact), it would be preferable to say: "A certain, ill-advised and badly produced way of Belting is unhealthy". No one who knows anything about healthy Belting would ever teach it the way he defines it. It creates much confusion and insecurity amongst singers who will then start to believe Belting is generally unhealthy. WRONG Belting is unhealthy.
Sorry I had to go on about that one for ages, but I hope it is now clearer.
Support: What I said was actually "not enough focus on", not "ignored". It is true that it isn't completely ignored, but Seth himself mentioned more than once that support is a by-product, and that it shouldn't be controlled directly. I completely disagree with this view. I will leave it up to anyone to do their own research into it though and then make up their minds whether singing is really a "relaxed process".
As for the zip: Great if you don't teach it and if it's not been taught to you (gives me hope), but it WAS actually part of SLS: Zipping refers to the very phenomenon that Seth used to describe as "thinning and shortening". His idea behind it was that at some point of ascending through our range, a shortening process starts instead of further thinning, making less of the folds vibrate in our higher range. This is simply physiologically not true. The bit he refers to is actually not vibrating in the first place because it's part of the arytenoids, but I'll again leave it to everyone to do their own research on the matter. At the time he constructed this theory, he certainly had the best intentions, but at some point, people just need to admit that their theories don't hold up. I can understand why someone is passionate about their own brand, but I think this should never lead to ignoring current vocal research. There's still a lot about vocal production/singing we probably don't understand, but some things ARE clear these days. Vocal science has done massive leaps through the last one or two decades, and we should adjust our teaching accordingly.
About myself (so you understand my background): In my work as a teacher, I think it is my duty to cater for the individual needs of each and every student. Since I teach both classical and contemporary styles, there is simply not one method that caters for all - only common sense. I studied classical singing to postgraduate level, I did extensive formal training in Musical Theatre (which included a lot of Estill and SLS, and all teachers were certified practitioners), and I studied different singing methods (again EVT, SLS, CVT and a few other, more obscure ones) in quite some detail over the years. Above all, I try to stay informed on vocal research and physiology as best as I possibly can. This is, for me, not possible through subscribing to any one method, because they all have their flaws. Some more, some less, but none of them work for every voice in any given stylistic context.
I can sing classically, "mixed", and I can also "belt" (including a few substyles), but if I have a choice, I actually prefer "mixing" (I really don't like using these terminologies, because they mean something different to everyone). I am not a particularly "tense" singer, and I am used to very fine muscle control, especially from my time as a classical singer, so it's not a question of building up subtle use over shouting or forcing in my case.
I just have a very inquisitive mind. I am always sceptic if something is hailed as the holy grail. It is quite interesting that over the years, even amongst certified practitioners of different singing methods, I came across two kinds: The ones who get defensive if you question parts of their methodology (and those ones ironically very often won't/can't explain the scientific reasoning behind it), and the ones who are open and accept that there is no such thing as one method that knows it all, and who are even able to admit that their method has flaws - it is just the one they personally feel closest to because it provides them with the best individual results.
Whoa, that was long, but I love these discussions

Edit: Oh, I forgot Amy Lee.
Yes, but that's exactly the problem (the sound example you picked is alright-ish, but one performance doesn't mean there's no problem, and "Bring me to life" is generally not one of her riskier songs). She normally uses a more "mixed" sound, which I really like btw. Every so often, she will attempt a thicker sound though, and that's where it goes to pot. That's, as I tried to explain, not an indication for SLS generally being bad (because she clearly does something they wouldn't subscribe to), that's an indication for it having its
limitations, and not serving the singer for everything they want to do. If she wants to create a thicker sound without pitch problems and strain, she needs to resort to a different technique.
http://www.youtube.com/watch?v=r1kTcfzyHAohttp://www.youtube.com/watch?v=f-TQ-Fs6ykII left the one titled "Amy Lee Screwups" out, because I think that's mean.
As an aside, which I mentioned earlier: Hardly anybody belts through an entire song, and "Belting" alone means as much as "Chocolate" - that's why I called it "belt-style", because there are many different set-ups people will refer to as Belt, and they have little in common apart from being called "Belt". Amy often uses something people refer to as "Pop-Belt". CVT for instance would call it Curbing, and in EVT terms, it is not a regular Belt either - more a Speech/Cry Mix, or very occasionally a Howl Belt, if you want to use the modifications Gillyanne Kayes made. She is doing better where she sings thinner, you can hear it in both songs. As soon as she tries to sing thicker in her higher range, she simply doesn't know how to approach it - that's where SLS can't really help her, because it's against their philosophy so to speak. So the question is: Should she choose to not sing like that, or should she find someone who can teach her how in a voice-preserving way?