There seems to be a running battle between shooters and hunters over which rimfire is best. I have both and find uses for both of them where they outshine the other. I do not really understand all the arguments and hostility. I will try and give you a common sense explanation from my experience of what I have found for each round. I recommend you go to Hornady, Federal, CCI and other ammo websites and read about each cartridge and what the specifications are at different bullet weights. I am really impressed with the new Hornady 30grain .22 WMR round as it gets the speed and flat shooting of the cartridge almost up to the .17 HMR but with close to twice the bullet weight.
I have found the accuracy of the .17 HMR to be superior to the .22 WMR in nearly every firearm I have shot it in. It is flatter shooting and has better long range accuracy as it is affected by wind drift less. I have found the .22 WMR to be superior in impact and knockdown in almost all cases. I have killed, as have many others, game that I would not have shot except under ideal conditions with the little .17 HMR. I have also lost a grey fox that was hit about two inches behind the shoulder at thirty yards. I have seen marginal kills of prairie dogs at long range with both cartridges but more with the .17 HMR. That could be because I can hit them farther out with the .17 HMR as I shoot it more on prairie dog hunts because of less wind drift and better accuracy. You can not beat the .17 HMR for a day of gunning jackrabbits or prairie dogs with a rimfire cartridge.
The bottom line is that both cartridges have a place in my gun safe. I find that for long range varmint shooting I tend to pick up the .17 HMR. For fox size and larger predator hunting I pick up a .22 WMR and pick my bullet for the task at hand. I have seen to many well shot coyotes and cats run after good hits at long range with the .17 HMR. They may have been dead but they were not recovered. If a bobcat or fox makes it to a brush pile or hole it is lost. I want to anchor them where they stand and find I need at least .22 Magnum performance to consistently do it.
I think if you honestly evaluate each you will find you need at least one of both calibers.
Good Shooting, Wild Ed