Finding "the healthy medium" Sassy spoke about is key. For every study that says one way is "best", there are probably a dozen others saying the exact opposite. Part of training is periodically changing your variables, so you could experiment with different schedules to see what works and what you like.
I really like my 4 day a week schedule. I think of it as a "work hard - rest hard" plan, because even though I go balls to the wall on my training days, it gives me three complete rest days on Wed, Sat & Sun. I do about 45 min of weights first, followed by 30 min of cardio, then 15 min of stretching. Twice a week my cardio is HIIT intervals.
Whatever training schedule you have, it's always going to be a balancing act between results, injury prevention, and mental freshness.