I was wondering the same thing in recent months... I opted to go heavy heavy and keep my reps low on my dedicated "arms day". I alternate the exercises, but typically stick to my "basics"... For bi's i go for BB Curls, Incline DB curls, preacher curls, reverse grip easy bar, and perhaps an occasional cable, every few weeks. (Not all in one workout... i'll do about 3 exercises, 3 sets of 6-8 after a warmup).
For tri's... i go as heavy an humanly possible on v-bar cable press downs or weighted close-grip dips, rope extensions, tricep kickbacks using either DB or the cable, overhead DB presses, or reverse grip cable press down (target a different part of the tricep head)...
I've seen a solid 1" increase in my arms in the past 2-3 months... So i'm satisfied! It could have been a bigger increase, but i am doing a VERY lean bulk, and trying to slowly reduce my love-handles while gaining mass. If you are in an all out "mass gaining" phase... then you may notice better results. Afterall.. nutrition is everything!
Hope that helped.. Have a good one!