IM Sure buster is writing this up in much more detail, he seems to he hovering around
PCP (Pre charged) Is a cylnder under the barrel, that is filled from a buddy bottle or pump, get quite a few hundred shots per charge, and only needs cocking via the bolt to open the breech.
Spring as you know needs to be cocked by brakeing barrel and inserting pellet.
PCP's are a lot quieter and can be shorter.
Go for PCP
If im wrong in anyway, please feel free to correct me...
Good hunting
paddy