I understand why they made these changes for Gen3 - It's a clear reply to the S&W FPC, and probably a smart marketing move on that front. But I don't see the Gen3 changes as necessarily an improvement on the Gen2 Sub2000.
The biggest reason is that the only time I ever fold my Sub2000 is to clean the barrel - Even with a fixed optic, the Gen2 folds open well enough for that. So for me the rotating handguard has no value at all. It adds expense, weight, and complexity. I get it if the folding feature is the primary reason you want a PCC like the S2K, and if you need a quick-deploy optic at the same time, but for many people it's a wasted feature. The Gen2 Sub2000 doesn't need to fold to be an outstanding PCC option - It's a super light, super slim, excellent handling, well-priced, Glock mag compatible, non-restricted 9mm rifle.
Next, going to the shorter grip (to allow G19 magazine fitment) means that G17 mags will leave a gap between the bottom of the grip and the floorplate when inserted. Unless you're really into the G19 pistol, this isn't an improvement. The G17-length grip on the Gen2 isn't that long to start with.
I do like the charging handle upgrade though. It looks easier to operate (I never had a problem with mine in factory format, but I can understand why others might). And giving it a hold-open catch on both sides of the tube is smart, for sure. I generally like having more rail space available, but honestly this type of rifle probably doesn't need it.
Unless there are other improvements we haven't heard about yet, I strongly prefer the Gen2 Sub2000 over the Gen3. I really hope they keep the Gen2 in production, but they probably won't. Maybe it's time to buy a spare Gen2...