The OP mentioned groundhogs, which are MUCH..much larger and more wary than gophers are. Groundhogs can be taken with 17HMR but having shot lots of them with both 17HMR and 22WMR, I will say that 22WMR is significantly more effective on them. 17HMR really demands a perfect shot to be a humane kill on something the size of a big groundhog, 22WMR seems to be more forgiving..which is good. It isn't as accurate a caliber to begin with. lol
Based on the OP's thread-starter, it DOES sound like 17HMR would be the better fit of the two for sure. 17HMR is very accurate/flat shooting out to 100+ yards, and pretty capable from a varmint hunting POV. Depending on where groundhogs fall on the priority list, it's worth exploring how your rifle likes the heavier 20gr. hollow points. Like any rimfire, figure out what ammo IT likes...and just run that. Even if it's a ballistic tip like Hornady 17gr., you're better making a great shot with an inferior bullet type than a so-so shot with a 20gr HP. For targets the size of gophers~17gr. BTs are exactly what you DO want. They dump most of their energy instantly, so less risk of flying lead after hitting such a small target at such high speed.
So to sum-up..
17HMR~best for speed/accuracy, probably the easiest rimfire caliber to get the best accuracy results from quickly
22WMR~sort of the clumsy, more powerful big brother of the .22LR

Nobody I've ever met picks this caliber for target shooting, but for 100 yard varmint hunting=very decent
FOR groundhog hunting specifically, about the smallest...most capable caliber I've used (to good effect even 2 days ago

) has to be 17 Hornet~which is a centerfire of course. Only seems a bit louder than 22WMR, zero recoil, and deadly out as far as I've pushed mine~198 yards. I do still keep a 17HMR for my western gopher trips (never use it here in Ontario) and while I don't currently own a 22WMR, I'm planning on getting another in the not-too-distant future. Will probably be a Savage B series heavy barrel. I would pick a CZ if I had even a shred of faith the extra $ would equate to better accuracy. Just hasn't been my experience that any gun shoots 22WMR exceptionally well.