I 10 box and in 2 5 mans at the same time. Prot pally in one and prot warrior in other. With the war I put 2 healers, and the pally just 1. Comparing tanking. The pally is just easy mode in ae encounters. But, single traget bosses he has a hard time keeping agro, especially with mobs that switch targets regardless of threat. I find both are great tanks, but with war you need to sit back at first before you burst out dps, and with the pally, you can usually just go nuts. My war can outlast the pally team in the long run.
In the end, it depends on what you think your going to be doing the most. Bosses or ae fights- but both have there fix to it....IMO lvl them both up lol.

Sorry for the spelling, wrote it on my blackberry lol