I'm no expert at all, but I really enjoyed firing pistols chambered in 9mm and .45. My all time favourite pistol to shoot thus far has been the 1911.
My advice would be to go to your local range (with your buddy would be even better) and rent some of the different handguns they offer. This can give you an idea of the calibre you are interested in as well as the general feel that you seek.
Having never owned any gun I can not comment any further than this.