I encourage you to look at the Beeman R9/Weihruach HW95. In my opinion, this is about the perfect balance of weight, power, cocking force, firing behavior.
The 48 is simply too big and stout for extended shooting comfort. The modern HW50 packs too much power into too small of a package so you get increased cocking effort and harsh behavior. (The previous 1960-'80s version of the HW50 was a pussycat, however).
With spring guns, it's a mistake to chase power. You should be looking at firing behavior, smoothness, etc. You've got to find a balance of power, size, weight and cocking effort. You don't get that when you try to push the limits.
As for caliber, I prefer .177 and that would be my choice in either the HW50 or HW95. For the 48, I would stick to .22 though. You'll need the heavier pellets to calm the gun down.