When you were a kid, where in the roller coaster did you sit? I always went for the front car...
I not only like the look of the std 2 piece, but find it sufficient..others say that the one piece gives better wind and rain protection, but I 1) Wear goggles, and 2) Don't drive in the rain.
I also like the idea of being as out in the open as possible, so the extra air circulation..even with head and eye gear...gives generally more of the front of the coaster effect.