To be honest, I don't know because I never tried.
Engine#2 was created in order to go around the 64MB limit in XP, and was therefore a kind of emergency solution.
Note that Engine#1 was created, awaiting Vista back then, and was therefore a kind of emergency solution just the same.
In either case I met all prerequisites to squeeze the best sound out of them (IOW no compromises), but also, both are not bit perfect.
In Vista this is even worse, because Vista in Shared Mode always resamples (even from 44K1 to 44K1).
You may try to listen to this "test" :
Test track with distortion which isn't there... , although it would be good to have the reference first. Note the "reference" is about a very clear distinction between hey key piano notes and bells, which in Vista #1/#2 get mixed in piano notes with bell harmonics.
I recall that XP is okay even at Double (Engine#2).
You need to be in the speaker with your ear, or must be able to play very loud.
Anyway, you might perceive a difference between #1 and #2 under Vista by this means, and make your choice this way ...