Both.
I have guns that I bought for practical purposes (kel-tec pf9, taurus 605 .357),
guns that I bough for the "cool" or collector-ey factor (luger p08, SVT-40)
and guns that I bought for a combination of both, which consists of the majority of my collection (1911s, S&W revolvers of various makes, cz82)
I like classic and collector-ish stuff, but the brunt of my collection consists of nice classic guns that also serve a purpose and get used. I wouldn't say they are bought mostly on impulse, but I wouldn't say I researched and planned to buy most of them either, it's usually just a nice combination of a good-great selling price, my knowing what I'm looking at, and having money in my pocket when a good deal comes up.