From: Zagreb, Croatia
The 88mm shell would do more damage, but the 75mm L/70's quite a bit more accurate and was easier to reload (lighter, smaller shell) and as such had a somewhat higher rate of fire.
The Tiger's turret rotation speed, or turn radius in general, was also slow as cpt flam noted.
Also, IIRC, the 75mm Panther shell was higher velocity than 88mm Tiger I shell...
Prior Preparation & Planning Prevents Pathetically Poor Performance!
A & B: WitW, WitE, WbtS, GGWaW, GGWaW2-AWD, HttR, CotA, BftB, CF
P: UV, WitP, WitP-AE