ATL is most logical time/direction wise, but if you are looking to maximize miles, DL has done a really good job with their setup at LGA, especially given the LGA space constraints. I'm quite a fan of their LGA space.
Of course, a passing storm, low clouds, winds, or a scattering of mosquitos can tend to back LGA up and destroy the best laid connection plans. If you have the rsk tolerance, though, and want the miles, then go for LGA.