Short answer:
If you want HD, it is generally thought that Dish has better quality and more HD than DirecTV.
If you want sports, DirecTV is the one.
Longer version:
Both have issues regarding installs, this varies from experience to experience, so any thoughts here would tend to be subjective.
SD quality on either is also subjective and is dependant on equipment (i.e. TV size), and optical accumen of the viewer, as well as subject to individual expectations, however, it is the general consensus that Dish compresses the signals less than D* and thus has a better quality.
Package selections are different, and would be subject to viewers tastes, i.e. international programming, some prefer E* to D*, some prefer D* to E*, prices too depend on package selection.
Hardware, I do see on the forums here more hardware issues overall with Dish than with DirecTV, I myself have D* and the hardware (SD D10s) have been pretty well behaved, I can also say with confidence my D* picture beats analog cable hands down where I am, especially (SD) locals, as for DVRs, others report the Tivo based D* dvrs are good, depending on the model, with varying degrees of satisfaction, the HR20 is yet to be released.
Hope that helps.