It varies between composers. I'll chip in a few bits and pieces based on my experiences

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For Bach, I like the Neue Bach-Ausgabe published by Bärenreiter. Not only is the music well type-set (large pages, crisp writing - makes AB editions look smudgy and cluttered in comparison) but as much of the original notation for ornaments etc. is preserved as is reasonably possible. The result is the odd squiggle that one wouldn't find in other editions, but the big advantage is that one isn't tied into playing what a modern editor thought a given ornament should be played as - one can do anything that fits Bach's original intentions. There also aren't any fingerings written on the score, so I sometimes cheat and look at what is suggested in the AB edition - or the 'playing with stabilisers on' edition as I call it

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For Beethoven, I do quite like the AB editions but recognise their short-falls - student editions, as you say. I cross-reference with the Henle edition if I'm learning something properly.
Chopin - Wiener Urtext. If only for the flexible binding that doesn't close itself on the piano

. Seriously, though, it has plenty of alternatives given when the sources were conflicting and is a good scholarly edition.
Scriabin - M. P. Belaieff. Scriabin's publisher, so I thought it seemed quite fitting

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