If I remember correctly, Phil, although the spring may well be the same, the top hats will have different dimensions, increasing/decreasing piston weight and preload, as you describe.
OP - although many don't have an issue cocking even the .177 HC, if lighter cocking is desirable, maybe consider the .22 full length version?
But, as Mike says, better to try a few out (maybe even different makes if you're open to that idea).