I think one should "worry" (consider) everything - application, ergonomics, weapon, caliber... It is VERY important to not only ask questions but also read - there are lots of info on application, ballistics, .... when one decides to get a gun, ammo, ... it is important to research and know everything you can about the platform you are getting, the ammo you are choosing.... The are many boards on the web dedicated to particular firearms, choice of gear, application, ammo....you name it. Sometimes, many I would say, the "popular" stuff is not the best choice, just better advertised. I usually look what professionals use and what they have to say - professional shooters, special ops, special forces, SWAT...