Hi Jake,
I fish with a VS250, sometimes VS150 and I agree on the stiffness while cranking. The ones I have are not the smoothest (but I am OK with the amount of reel stiffness). I treat the reels rough, submerge them, sand. Not nearly as much as you, but I know of no other reel that would stand for the treatment I give them (with the exception of the ZB).
I am extremely happy with the Van Staals (they meet my expectations).
I read a few complaints on the ZB (last year), that out of the boxes there were problems and they were fixed by the manufacturer.
I think the ZBs cost a few hundred more that a VS. Also how stable is the company that makes a ZB?
Sounds like based on your report, the ZB you have is better than a VS (reliability in rough conditions the same, exceptional smoothness of the ZB).