You are going to hear a somewhat greater difference between a T4 style and a T4 style backwards converted for a T3 or S910 than you have had in the past, I fear.

SA voices in a style is a considerable jump in technology (mind you, Korg has had it since the new OS update, and I have no doubt Yamaha COULD have done it with an update for the T3, too, but that's not the 'Yamaha Way' ) and the style itself will contain much data specific to the SA triggering that will not be relevant to the T3/910.

Add to that that MANY of the new styles use the new vocal sounds (overuse them, IMO) that the T3/910 doesn't have, and the new kits... I can see a while before they figure out how to make these backwards compatible...