Dear Miss Snark,
You've made it perfectly clear that an agent needn't reside in NYC to be effective. The flip side of that question: do you think there is any advantage in having an agent geographically close to to the author? I can't imagine what difference it would make, but I get a little thrill when an agent's address is similar to my own.
You need to get out more. Seriously.
This is akin to picking a runner in the 4th at Belmont cause you like his name.
Effectiveness is not a function of geography. There are some crap agents in the 212 and they aren't going to be any more effective if they move to Buncombe County, North Carolina.