Just my 2 cents but I haven't heard of too much trouble with the zippers on Stohlquist suits, my buddy has one and is happy after a few heavy seasons. I have a Kokatat and couldn't be happier (or warmer) but the Stohlquists seem to be good quality for better price, as long as you don't get neoprene gaskets. In the end, I think the rubber on the outside isn't doing JACK. It's the zipper design and how tightly they seal inside the zipper that matters.
Some engineer out there might challenge me but I think any (open-able) waterproof seal needs to be under pressure to work well. The rubber on the outside might reduce abrasion with other gear but I bet it doesn't appreciably contribute to dryness.
*caveat* neoprene gaskets probably work GREAT for rafters. But not for kayakers.
"Paddle silently, boof loudly"