The system has a large influence. In 2e it was almost all character concept. In 3e it was mostly character concept, but I'd tweak my choice maybe a bit. In 4e, optimization plays a big role in the decision. I think this is because of what the system validates as "cool." In 2e, the system really got out of your way because there wasn't enough substance to get *in* your way, so you made yourself "cool" by what you chose to do. Third edition put more substance into the system, but the character customization process was still a composite of a dozen or more little systems of which race was just one (minor) piece. By 4e, the system had a lot more to say because more events happened within the confines of the system, and, as a result, the system mattered more. The vast majority of my decision with regards to race in 4e has to do with stat mods, because stats in 4e matter so much.