Every spec I've ever read says that I should ride a 134 to 140 twin tip, which is what I've been on from my first day on the water. Recently I've switched to a 129 and I can't say I'd ever ride anything bigger again.
It seems to be the difference between a longboard and a shortboard for skating and surfing. Are there any disadvantages to riding a board much smaller than the board my height and weight is specked for? ie less pop, less height in big jumps, more face spray, harder upwind, etc? I haven't noticed any of the above but I am still a beginner/intermediate rider.