glock 19
glock was originally a 9mm, and they just modified the 9mm over to 40cal when that cartridge became popular, as a result it is most durable and accurate in 9mm, and the recoil with the 40 glock bothers some people
i have 115 grn +P+ law enforcement winchester rangers in mine-that's another plus, the glock 19 can take +P+ all day long
the glock 45's are based on the 10mm glock which came out first, strangely enough. as a result they are way too wide (built beefy to handle the high pressure 10mm).