I think a mix is best. Heavy bb and db curls, then some machine and cable stuff to finish.
That's the standard thinking, but also try going against preconceptions and consider cables for size. Go as heavy as possible for moderate 6-12 reps.
Debunking the Barbell CurlRonnie Coleman
I never advocate the use of the exercises cited as the kind of mass building for the biceps: the barbell curl.
Like everybody else, when I started bodybuilding, I waned bigger biceps, even tough I am blessed with good arm genetics. I though the route to follow was doing barbell curls, but my early experiences with that exercise taught me that although barbell curls allowed me to use heavy weights, the muscular stress caused by the poundage was in no way being applied 100% to my biceps. I believe that the heavy weights employed for barbell curls encourage the user to cheat through the exercise, perhaps without even knowing it. A person tends to bend the upper torso to let the momentum of the weight take over. In addition, instead of the biceps powering out the reps, forearms and front delts are called into play too much.
You must analyze what kind of development you are aiming for with your biceps training. You should seek full development in terms of thickness and fullness of your biceps muscle attachments, plus optimum accentuation of the biceps peaks. Those aspects are best achieved by exercises that isolate the biceps - ones that allow you to put maximum stress on your biceps throughout the completion of each set. Cheating on barbell curls means that at certain times during the course of a rep, the biceps are given an easy, if not free, ride.
Based on the preceding thought, I came to the conclusion that cable work provided the required dual facilities of isolating the biceps while allowing them to be under constant stress throughout the completion of each set. The latter element is particularly difficult to attain during the negative (descending) part of each rep. This is where cables score heavily. With cables, you can maintain muscular stress during the negative phase to an extent that is not mechanically possible with free weights.
Many authorities claim that cables are solely for advanced bodybuilders, in order 'to refine what they've already built.' I don't agree. Cable work allows you to attack the biceps with 100% concentration, and that sort of exclusive application will make the biceps grow. Muscle fibers don't know whether the stress is being applied by free weights or a machine; they respond only to the level of muscular stress being placed on them. Whatever does the job, will do the job!
Ez bar curls on an incline bench, facing backwards like a rear dumbell fly, arms hanging straight down and crimp the hell out of your bis If you do it right i guarantee you'll love it.
Spider curls. I don't use em but they will hit your bis from a different, extreme angle.