I agree, Taichi may be the best suit money will buy off the shelf. We had one racer a couple years ago who crashed 17 times in one season in a Taichi suit and it was still wearable at season's end. You just can't beat that for performance. Then I have seen some suits that came apart at the seams on the first crash. I wear a Taichi suit as well for the track.
A suit vs two piece? The suit is better for crashing only because it can't seprate in the middle and give you rash on your belly button. However, if you buy good leathers in a two piece with a wrap around zipper, they hold up quite well too. I've never seen a crash with in a two piece that zips together where the suit separated at the midsection.
I prefer a two piece by far when riding on the street. I have pockets to put my cell phone, bike key, wallet, comb, etc. etc. and best of all, on a hot day I can pull the jacket off, throw it out on the grass and take a nap if I want. The suit is a pain in that department.
It's all a matter of preference and you can't go wrong either way. Taichi is a great choice either way?