I've seen a lot of differing opinions on this, but no real explanation behind them. Personally I think minutes are better. Slower runners (like myself) will be spending more time on their feet to run 100 mpw than the next guy, which seems really conducive to injuries. It really comes down to effort levels and how long you're out there, so how many miles you complete in the process is really irrelevant, right? I may be wrong though, this is just my mildly informed opinion.
What do you guys prefer/use, and why?