I use OB Pro shafts; I have two shafts for my player, the original 29" that came with the cue and a 30". The only difference I've noticed is that I have to grip more towards the butt of my cue more with the 29" shaft. With the 30" shaft, my grip is typically at the back of the linen wrap. Also, with the 30" shaft I don't have to use the mechanical bridge quite as much.
The two play exactly the same to me. I don't think there is any deflection difference, they feel and sound the same and I haven't noticed any difference in balance. Maybe there are differences and I'm not quite good enough to notice.
Is your 30" shaft of the same make as your 29"?