The CP1 comes with a steel breech as standard, while the 2240 out of the box has a plastic one. Both can be modded to various degrees, but for a starter gun, he may do better with a metal breech from day 1. Possibly an idea to (if possible) try handling both as the CP1 grip is larger than the 2240 one. If you fit an adaptor for a silencer, you should still be able to use open sights by
a) 2240 using one of GMac's adaptors with an integral foresight pin
b) CP1 getting one of porkyyorky's silencers off the UK Chinese Airgun forum that have a built in foresight pin