the P1-HW45 is a spring powered gun and it cocks with a motion to the front as you open and that makes it easier to cock
has felt recoil and can be harder to shoot for some, they come in full grip frame that can take any 1911 grips, from just panels to target grips from say Herrett
of course the HW45 come in a half grip frame in there special model and of course as stated the HW45 has more power
the HW75 is a single stroke pneumatic and it compresses air as you close the top half of the pistol and this makes it a little hard but the HW75 is easy to cock vs a P17
there is no felt recoil in the HW75
the grip frame on the 75 is a half grip frame and takes only the grip that come with it but you would find they have a nice feel in the hand
both pistols are the same size and weight gave or take
so with no recoil the 75 can be easier to get on target but that is up to the shooter with both pistols
one thing you can do with the HW45 is change out the barrels to .20 and .22 if you buy the .177, it take some doing but that's another story
the HW75 came in the old Beeman days with a full grip frame and was a P2 and it seems Beeman would do a half frame mod to take half grip frame grips
well that's a start
take care
mike