Personally, NYC area has better flights w/ DL and US airways. CO only counts on EWR travel.

Price compare to AA vs DL/UA, DL/UA is much better both in route and price.

LGA is best place to go to in NYC area.
JFK usually have better price, but also depends on the route.
LGA has DL shuttle.


Flying DL/UA out from JFK/LGA is best choice IMO.

If you use AA cc on everyday spending, just get another DL cc, use only to purchase ticket, still use AA for everyday spending for 1mm on AA(might take you longer tho. :P).