MY reason is a matter of evolution.
I had D* first when they first came out and added E* when they added Showtime HD. That was in year 2000. Since that time E* has always been the leader in HD programming with more variety. E* also had the first receiver that was compatible with a DVHS HD recording system. Then they solidified that lead with HD DVR. But that was a 921 which had lots of problems and limited storage. Then came the HD TIVO with swappable main hard drives for huge amounts of storage but that was only on D* so I gave the bulk of my programming $$$ to D*. That lasted until E* came out with the VIP 622 and added a boat load of HD channels with the Voom network and others. Since the VIP 622, I have switched the bulk of my programming back to E*. Presently, I have no good reason to stay with D* except to follow their promises of "we're the leader with future 150 channels etc. So, while I still have the HDTIVO, I can't get any of D*'s new MP4 channels, but why would I? Nothing they have announced satisfies my interests that is not already on E*. In addition, the latest upgrades to the VIP622, with unlimited hard drive capacity makes it a superior design as well.
As far as the money goes. I had a fixed budget for TV programming- It was a good budget that allowed me to pick one major and 2 minor competing packages. When VOOM went down, I freed up that portion and to do a modest D* plus everything pack on E*, I had to drop Comcast as well.
I do have both D* and E* but my D* is basic cheapest SD and the HD pack as an add on. While E* is everything package with HD.
I don't need NFLST with HD since I can see all the NFL games I'm interested in for free, If they are blacked out then they would be blacked out for NFLST as well so that sports package, IMO and in my case is a ripoff.
Soon when I see the outcome of D*'s 150 HD nationals next week as promised, I will make a determination if they have anything better that would prompt me to switch back the bulk of the progamming again to D*. But I am capable of prioritizing those in the list. IMO, getting TLC HD and Science channel HD would way out weigh adding QVC in HD if you know what I mean.
So if DirecTV continues their ad con game as they have been doing for the past couple years, I may indeed drop them altogether and save myself $56 per month.
Please understand, I don't favor one over the other, ever. However, it is a fact that E* offers better customer feedback than D* and D* doesn't have a monthly chat program both marketing and technical with CEO and VP and other engineers, ad people and programming. Under the old management, D* would never talk about future plans. Today they talk too much and don't follow through.