Hi,
Good luck with what would be an extremely expensive quest here in the UK. Although I have both calibres for this pistol, I would certainly go for the .177 given a choice as I find this much more accurate at 10 metres than the .22 calibre.
Interestingly, I have found this to be true for all spring powered air pistols I have tried with the reverse seeming to be the case with my Co2 powered pistols (Crosman 150, Benjamin 262 etc).
Regards
Brian