Wow..tough ask, I pursued the T4 for two years before I could get my hands on one, it's a great arranger no doubt about it, but since the A5 arrival I think I really enjoyed the sounds out of it. With my current PA set up now (HK elements) , the sounds / styles are just so LIVE and surreal. I literally get zoned in and buried in it. What David said below is completely true. The T4 has great and I mean great variety of styles and voices but its midi and very CD like quality as oppose to the live sounding works of the A5. So to answer your question. A5.... But I guess, knowing I have the privilege of both its much easier to chose one over the other. For me , music is like watching a great movie. It should really take you away from the moment. The A5 does that more for me...Ky.