unless your going to use it to hunt i would go with a 9mm they have a lot of peneration and low recoil also likeUSNRETHunter
said they have alot of rounds in a small package i had a ruger p89dc good price gun and you can shoot through alot of stuff with it alot of people say the 45 has more knock down power but what a little more knock down power when you can but 15 round factor clip trough a center block wall and in your target 150 round does not leave much chest leave to breath with or pump your blood to your brain but for self denfense there both good also the 9mm rounds are cheaper if you look you can get 1000 online for around 100 to 120 dollars