I have both .17HMR and .22WMR rifles. I'd go with the .22WMR and keep my shots at 100-125 yards. With the new ballistic tip ammo both of my .22WMRs perform very well. I just think the .17HMR is a bit light for fox and the damage it can cause might ruin the pelt. Perhaps the .17HMR in a hollow point 20gr round might do better, but both of my .17HMRs are far more accurate using the 17gr Hornady pills. The .22WMR will give you a heavier projectile wichh can make a difference on game larger than rabbit, or squirrel. I realize there are guys out there hunting animals larger than fox with the .17. I prefer to not take the chance of wounding the animal rather than dropping it quickly. Besides, that's why we have more than caliber in our gun safes.