I've had 1 and 2 piece suits. Like the 2 piece. Profox makes a really good -15 suit for the money. $900 for suit and jacket, and they offer a lot of over the counter sizes so you can get a good fit. Has sewn in arm restraints. They also recertify their products. Not too thick either. Seem to have most if not all sizes in stock.
I've been on fire and got burned. Burns are some of the worst and most painful injuries to recover from. Spend the money and get good protection.....even if the track doesn't require it.