I'm on the fence about going back to EI through Direct or continuing my MLB.TV subscription
MLB.TV Advantages:
Price (about 1/2 of that of EI)
More viewing device options and streaming options (mobile devices, tablets, computers, PS3, AppleTV, Boxee, PopBox, and several TVs)
Archived games (can go back to watch any game of the season)
Available during the off-season, preseason, and post season
More games available for viewing
Easier to get around blackout rules (using a location spoof on my iPad and iPhone I can watch any game, even out of region Saturday games)
PIP and options for 1, 2, 3, or 4 games at one time (although you lose HD when viewing more than 1 game at time)
EI on DirecTV Advantages:
Don't have to switch devices when switching between games and other channels
Game Mix (much better game mix channel)
Not dependent on bandwidth restrictions, internet downage, or some hacker ruining the PS3 (like they did last year during the season)
PQ (the picture quality through DirecTV EI is better, but the difference is more dependent on bandwidth and the device you use to stream MLB.TV). The PQ on the PS3 was almost just as good as that through DirecTV
With my SlingBox I too will have more viewing options for EI on DirecTV, but I am unable to access my SlingBox through my work's server. I can access MLB.TV on the server though.