If your travels take you to NYC and DC from IND, (And I know im going to get flack for saying this) but take US. The US operation out of IND is top notch (again, not saying much but..). US has a much bigger operation than NW from both LGA and DCA, which will enhance your options if you need a reroute. Plus of course, the star alliance beats the sky team 100 times out of 100. For these 1 hr flights, USairways is just as good as the next guy. It is also worth mentioning Northwest mainly uses the CRJs (which are absolutely awful) while USairways is starting to utilize E145's, 170's and 175's which are the best RJs on the market.

Just my two cents...

PS I cant believe im defsending USairway