Matthies, I understand your point. However the OP stated that he wants biglaw, so I gave advice based on that. Plus if the OP would rather have a biglaw job outside of DC rather than a non-biglaw job in DC, Columbia will do better on that front. If the OP is biglaw or bust, between some info from the career office and previous transfers he should be able to develop a strategy for searching for a big job in markets outside DC.
Being in DC has advantages, however if the OP is thinking govt work as a back up, he should be aware that many fed agencies do not hire fresh grads, or that they hire through an extremely regimented process where they get tons of applications then only hire a handful of graduates. Look at the Arizona honors program handbook for more info. Your school should be able to give you a password to access it.
In general, I would still go to Columbia over GULC even for DC. DC is flooded with GULC grads b/c of the huge class size, and I think the added prestige from Columbia would confer a significant advantage. Networking in DC will be tougher, but not impossible from NY. I do not know if Columbia has a "semester in DC" type of program, but that might be something to look into.