I have been a member of a few "open 24 hours" gyms now. Unless you lift at odd hours, it is a benefit you won't use (so don't pay more for it). Usually, 24 hours gyms are the more commercial type - so the atmosphere sucks. My advice, go where there is decent equipment and a great atmosphere to lift all out (I personally like dim lighting, kinda dirty, decent amount of mirrors, low ceilings, etc).