I chose Walgreen's initially, and this was a 700+ a day store. Super busy, but the days just flew by, no chance for boredom.
While taking classes, a store like this would be impossible though, but I was lucky to find a Walgreen's that averaged about 50 scripts a day and had extra hours to give out (did not last long, but I rode that gravy train as long as possible). This gave me the opportunity to get paid to study, at least for the semester or so that the hours were available.
The point is, busy stores aren't necessarily a bad thing if the work flow is handled properly with good techs and pharmacists. However, I'll take boredom any day over stress, so I'd go for the easy job with less pay. Plus, wasn't there a study that said no matter what you're paid, you won't be happy working at a place you hate?
Good luck.