I debated last fall over this same issue. I chose the rear rack so I can call haul 4 bikes for the whole family(thule) . I don't have strong arms so the idea of hoisting my bike on the roof, well I was worried I'd lose my grip and the bike crash and damage it(and I'm tall enough too) so a rear rack for me. I have another car that did have a roof system(we saw where it used to be) and I could've gotten one for it, but decided not to. The seats fold down nicely in that car, It'll fit the whole bike in there anyhow.

I had to buy a hitch too btw