well since nobody else has posted any info let alone helpful info.
I would stay away from barrel cocking if you want accuracy. Not that they aren't accurate but I know that the lever cocking are MORE accurate in general, I am sure there are exceptions.
If you want to kill stuff like grey squirrel, fox, rabbits and such, my personally choice would be a .22 cal, the pellets are easier to find than 20 or .25 cal and they hit with more wallop than the .177.
If you are after mice and rats and squirrels and rabbits, then .177 is fine
I done know about the difference between Beeman and RWS but from what I have HEARD Beaman is a beefier more solid gun, and RWS is a, prettier, more "well finished" gun.
Bottom line is if you are shooting anything bigger than a squirrel the extra weight of the .22 cal pellet will help out, it isn't necessary but helpful. .177 cal @ 1000fps will take out rabits, rats, crows, feral cats and even a fox with a well placed shot.
Buy the best you can afford and if you put a scope on it do not skimp on the quality of the scope. A Spring piston air rifle will rip a cheap scope to peices inside and out in a very short time.
If you are just going to stick with the open sites. well then disregard the scope issue
