I am playing Scarlatti's sonata in D K.535 for Grade 8 next June. I came by another edition of the score (Check it here), which i think is much better than the urtext provided in the exam book.

The ABRSM edition is totally free of any dynamics, which i think is harder to play from than other interpreted editions. Also, according to the ABRSM edition, the arpeggios starting from bar 5 should be played with alternating hands, which is not the case in the other edition, which states that only the last 4 notes in the bar are to be played with the left hand.

I don't know but - musically speaking - i think the edition i found is much better. So, i am asking can i use this and use its fingering and use it in the exam or i should stick to the urtext??

I don't think the examiner will notice !!

I think you are missing the beauty of the urtext edition. Generally, notation in the Baroque period is accurate in terms of the pitch and rhythm of the notes - dynamics and additional ornamentation are left to the performer. The edition that you mention has been edited much later, thus the dynamics and pedal markings etc. which reflect the performance practice of the time the editor lived. You should be cautious when reading from heavily edited scores such as this - but do pick out the good points that you think will enhance your playing but stay within the context of the style of the piece.

With regards to the fingering and which hands to use, choose whatever suits you best - as long as the performance is musical!

Regulations state that you may use any edition of the set pieces - I'd check it against the one given, though, just in case there are any bad editorial deviations.

This is quite right. Your other edition gives an editor's opinion on matters of dynamics. Just because the Urtext edition gives no specific markings in a passage, it doesn't mean "do nothing" with dynamics and articulation. If your other edition contains an idea you like then use that idea, but don't follow all its recommendations slavishly. Listen to contrasting recordings of the piece and listen at how much room for manoeuvre the performer has.

Having said that, any dynamic markings that the Urtext does contain should normally be followed as they are likely to have come from the composer.

I believe that matters of which hand to use and when are for you to choose*, no matter in which edition they appear. As my first piano teacher said to me all those years back when I asked which was the "correct" hand to play a particular note, "you can play it with your nose if you want, as long as it sounds right".

--
*There are some pieces where certain alternatives are frowned on in performance, but these are rare.

At this level you should be making more of your own decisions about dynamics in music of this sort.

I'm with the Urtext crowd on this one too (not least because I'm doing a Scarlatti sonata for my grade 8 harpsichord and the dynamics are irrelevant ).

Baroque music needs to be understood to be played well. Look at the score, work out where the climaxes are, where the cadential points, where any counterpoint is (although not so much in Scarlatti sonatas). Use this knowledge to guide your interpretation, don't just rely on one editor's opinion as to how a piece should be played. It's unlikely you'll play the piece well without understanding it; taking a shortcut by using a prescribed 'interpretation' is a false economy.

The ABRSM is quite clear on this, you may use any edition. Using an Urtext is something recommended ad degree level. The edition has been produced from the Autograph (where available) and contemporary source material. The editor makes it clear where different manuscripts differ thus allowing you as a performer to make your own musical decisions.

At grade 8 you should be capable of making such musical decisions.

I have two editions for the Mozart (B2), my teacher has another. His, the Henle Urtext and my second the Barenreiter Urtext provide extra insight. However I will be playing it off the ABRSM edition in the purple book as the page turns are in the right place!

I thought the Henle edition would have page turns in convenient places as it is one of their strong points? *I'm a Henle fan*
(Though I spotted a mistake or two in one of their editions which they will rectify in the next printing - they sent me a free book and classy music bookmark in return!)

Yes the Henle has lovely page turns, the best fingering suggestions, and is a beautifully clear copy. Unfortunately, that copy is Donald's and not mine!

Oh, what a shame!

I tend to always try to buy Urtext editions for any of my own performing music if I can - usually Henle, sometimes Barenreiter - but if I'm buying music for my pupils I tend towards the AB editions - still good, and obviously cheaper. I think of Urtext as the 'pure' copy. I once tried learning a Haydn piece from an old edition which was extremely heavily edited - the editorial markings were actually detrimental to the learning of the piece as they were very intrusive and distracting, trying to mark in every tiny nuance. It would have been far better to learn from a clutter-free copy and express the music as I felt it - it would have probably been similar in places to the editorial markings, but the difference would have been that any expression would have come from within, rather than without, so to speak..... (does anyone understand what I'm getting at???!!! I know what I mean, but not sure if I've explained it clearly... )

Yes I do know what you mean. If your students can afford it and the Urtext is available, why not suggest they buy it. I bought my barenreiter Mozart Sonatas book ages ago when I was learning a completely different sonata. I treated it as an investment, knowing that one day there woulr be others I would like to play.