Just resurrecting an old topic here - SLS is NOT at all anything to do with belting or stretching the lower ranges of the voice to reach the high levels - it does NOT cause the larynx to rise as the voice rises - quite the reverse, the central tenet of SLS is keeping the larynx stable in all voice registers and producing a supported tone throughout the range.
It is an excellent way to teach supported, well coloured tone and expressiveness with little effort (once you know how to do it!

).
I speak from experience of having had years of lessons with traditional teachers (all of whom just got me to sound more and more like every other classical singer with no expressive difference) before going to a teacher of SLS (which is based on the principles of Bel Canto singing) and finding that within a few months my voice felt free, light and the vibrato was natural (instead of the bleating nanny goat tremolo the other teachers were instiling into me).
My vote goes for SLS - especially for classical singers. Although it is very important to find an SLS teacher who has experience of teaching classical singers as a lot of them do only broadway or jazz and, beyond basic technique, wouldn't be much help.
Also be prepared to pay a lot for it - last count was around 90 GBP per hour when I left the UK.
Allan