I’ve owned and worn two Gore-tex drysuits, one a nontunneled Stohlquist (no longer made in Gore-tex), and one a tunneled Kokatat GMER. Also, a lot of different neoprene wetsuits, Farmer Janes, and tops.
Two important points:
1. You can use either a tunneled or nontunneled drysuit with either a surf ski or a decked kayak that has a sprayskirt.
* If paddling a decked kayak without the tunnel feature, more water will enter the cockpit than it would with a sealing tunnel on the suit.
* If paddling a ski, it doesn’t matter, for obvious reasons. But the tunnel won’t harm anything by just being there.
2. The more relevant factors that are keeping me from wearing my otherwise-wonderful GMER drysuits are these:
* The front entrance zipper and the relief zipper are toothed metal (seals well) without any overflap. Now that the only capsize/tossoff recovery method involves lying face-down on top of the ski, there would be scratching, lots of it.
* Also, the Cordura panel sewn over the seat and knees, which adds durability for sitting on rocks, will stick to some kinds of seat surfaces. In sea kayaks with either minicell foam or nonsmooth fabric tops, the suit did not allow easy sliding. This was a negative for rolling. It wouldn’t stick to bare ski buckets but might to pads, depending on what the pad cover is. With wanting as slippery a bucket surface as possible, this could be something you would need to work around.
I don’t have any experience with Paddleskins, but I have used mostly wetsuits more than I have drysuits, except long ago when just starting on sea kayaks. There is no question that a Gore-tex drysuit with appropriate underlayers is warmer just because it is dryer than neoprene. That is either while immersed or while upright. However, once you have a solid roll (decked kayak) a wetsuit might still be adequate for the limited in-water exposure. I would guess that it’s the same if you can quickly remount the ski.
I wear neoprene until the water warms up and then “regular” tops and bottoms after that. But we don’t get the kinds of dangerous conditions here that ocean paddlers do.