Consider that the pro questions asked here will attract enthusiasts, but not the other way around, as mentioned in this blog post titled Asking the First Questions.
The purpose of this site is for mechanics and do-it-yourself enthusiasts to ask questions. The name "mechanics" implies a more professional Q&A site than "garage"; therefore, mechanics makes better sense if we want to attract the professionals that will breathe life into this community.
Additionally, you asked if the URL should be something the community votes on. I think the decisions in all areas should be made by the experts. In the case of domain names, the staff are the experts. The community evangelists and community coordinators have a ton of experience and have seen numerous StackExchange sites fail and succeed. In this case, I'm sure they had a good reason, which may be similar to my above opinion on this subject.
Voting is for the domain-specific questions that the staff can't answer and that the community as a whole must answer, such as what the site is about and the answers to the questions asked on the site. Other decisions about the site, such as what questions are closed, are where the Moderator Pro Tempore group and the high-rep user groups make an impact. These are the areas where the staff has made it clear that the high rep users are the experts, based on the combined upvotes of numerous community peers over time.