Ey up and welcome.
have to say, I used 22 for years and years, very succesfully as well!.
Then I bought a Daystate Air ranger in 177 and was completely blown away by how accurate it was ,how hard it hit , basically just how lethal the bloody thing was.. As with anything shooting, it is all about shot placement and ,I know some will beg to differ, with a 177 that seems much easier to achieve.
Whatever you get it`s all about being competent and confident enough to hit tha kill zone time and time again. i am sure you will succeed whatever you decide but these are just my thoughts on the matter