For my money, Northwest on an A330 is the best SkyTeam coach product, followed by AF (at least until they start with 10-abreast on the 777) but none of the coach products are going to set your world on fire. However, from New York, I think the fact that the CO flight is non-stop easily trumps any difference in comfort.

To be honest, if you are using miles, you will be stuck with whichever airlines have availability and there is no guarantee there will be more than one.