I'm not answering this from experience in either cartridge, just what I've read, so please don't criticize me for this. I'm just trying to help.
I live in New Mexico where the Muley shots are around 200 yd's or so. If I had to pick one (and I'm a reloader.....) I'd chose the 7-08. I belive you have a good variety of bullet weights for the distance and can tailor a load to fit this type of hunt. I think I read somewhere that the ballistics of the 7-08 and the .308 are almost identical.
Just my 2cts
Travis