I prefer 3 sets of 10.
However, it all depends on what you are doing.
I almost always hit 3 sets of 10, however, i do tend to mess with things a little. Sometimes i hit 3 sets of 10 at the same weight, while other times i just hit 3 sets of 10 reps increasing the weight each time. NOTE: I have gotten my most growth, size gains, and strength gains from doing the 3 sets of 10 at the same weight.
Prime example: shoulders...did them yesterday.
Yesterday i was suppose to do 3 sets of 10 reps at 225 on military (behind the head, actually top of crown). I ended up doing: 1 set for 10 reps, 2nd set for 12 reps, and the third set for 20 reps.
However, lately i have been doing 135 for 10 reps, 185 for 10 reps, 225 for 10 reps, and then going to failure at 275, usually 7 or 8 reps.