I subscribe to both mlb.tv and MLB EI. You can't beat MLB EI, the picture quality is great and on D* if the game on the RSN is in HD then you get it in HD. You also get home and away broadcasts (for the most part). The only issue on MLBEI might be the padres this year due to the new fox agreement. I follow 2 teams and DVR most games to accommodate my viewing times. You MUST record games on D* using the RSN channel NOT the MLBEI channels. I have had issues where games are blank or you just get the D* logo for 3 hours on the MLBEI games.
I also sub to MLB.TV for the iphone streaming, spring training games, and archive (if i forgot to dvr a game, etc). The picture quality on MLB.tv is good but nowhere as good as MLBEI. I also have streaming issues from time to time even on a FIOS 20/20 connection. You also have the dumb 90 min rule, in which you have to wait 90 min to watch a game if the game has ended. A lot of the time for the west coast games MLB.tv does not monitor and will go well beyond the 90 min.