Re: Answer HoNESTLY!!!
Tough to answer this one. I bought a full-on hardshell for track days, but my textile cycleport Ultra II jacket that I always wear has a plastic/foam laminate one built in. The jacket is great for four seasons riding and has lots of the same type of armor in other places, but the back protector is not in the same league as the full-on race units. I've tried taking out the jacket's bp and wearing the full-on underneath, but that doesn't work well.
As much as I like the UltraII, it isn't quite as cool as a full mesh in the high heat, and since it is longer, the extra bulk of the length and all those pockets can be a drag at times. This year I'm planning to go with a short jacket in air mesh kevlar from cycleport to match the pants I got last year. The pants are great, btw. It's got a zip-together option as well.