Bruce, when I had my Classic I, I also eventually upgraded the armbase to one with VTA on the fly. At that time, there was no Classic3 arm per se so it was technically an upgrade from 10.5i to standard JMW 10.5. At that time, it also included rewiring the arm with Valhalla wire instead of the stardard silver wire that came with 10.5i.
Personally, I think it was mostly the change in the wiring that made the biggest improvement. Arm base with VTA tower is bigger, may be a tad more stable but I did that upgrade mainly for convenience of VTA on the fly and not so much for any inherent sonic benefit not contributing by ability to dial in VTA accurately with ease. Of course, this is just a guess since I made both changes at the same time.
Personally, I think it was mostly the change in the wiring that made the biggest improvement. Arm base with VTA tower is bigger, may be a tad more stable but I did that upgrade mainly for convenience of VTA on the fly and not so much for any inherent sonic benefit not contributing by ability to dial in VTA accurately with ease. Of course, this is just a guess since I made both changes at the same time.