Get the .22; it will be far cheaper to feed. .17 HMR in a pistol isn't very useful if you can't legally use it for small game/varmints and centrefire ammo can be reloaded for less than the cost of non-relaodable .17 HMR factory ammo.
I would still choose the .22 LR/.22 WMR convertible if not limited to range use due to the ability to use inexpensive .22 LR for plinking.