What's better: fewer sets of more repetitions or more sets of fewer repetitions?

It really depends on what muscle your trying to excersize and how, for example, if your doing four sets of 25 push-ups, your muscles have more time to heal, with 2 sets of 50 pushups, your arms have less time to breath/rest and it makes it more difficult to continue as you continue that set. If your doing a 100 push-ups...well that's just worse for you than 2 sets of 50 reps. Hope this helped you out a bit.