I don't want to be the skunk at your little garden party, but I am hearing some troubling things regarding the whole Hopper/Joey thing, in that the whole system is pretty buggy and frustrating to use due to a terrible search and program list GUI. The whole commercial skip thing is up in the air too; if they lose the lawsuit, which is expected, they will have to disable that. The question becomes can they disable the commercial skip without torpedoing other features of the DVR?
For DTV, if you want to archive programs, I think the best thing is to use an external or eSATA drive, and place that in a ThermalTake enclosure. The disadvantages are as stated here by others: recordings are married to the DVR so that they will not play on other DVRS, you can't see both internal and external drives at the same time, and it takes a reboot to switch drives. Unlike DISH, DTV does not employ any techniques where programs are migrated from one drive to another.
But other than that it is pretty easy to manage; to start from the internal drive, just power down the external enclosure and reboot the DVR. To start from the x drive, just power the enclosure up for about 30 seconds and reboot the DVR. You don't have to worry about connecting or disconnecting cables or any of that. It also helps to take cellphone snapshots of the program list so you can refer to that when booted from the other drive.
And if you want to have multiple drives with multiple archives, the ThermalTake makes that pretty easy too; just pull one drive out and stick the other drive in (and reboot).
I have seen reports claiming 585 hours of HD on a 2 TB drive. My real-world numbers have been closer to 475 the few times I have actually filled one up.
Finally, having been a subscriber for 8 years to each service (not at the same time), and having dealt with both services at work and for relatives, DTV impresses me as a much better run company, and that may manifest in less frustration when dealing with them directly, which subscribers unfortunately must do on occasion. DTV still leads in HD channels as well; be sure the channels you need in HD are available on DISH before you switch (if you do).
As for the OP, switching from DISH to DTV should be a mostly-positive experience. Some DTV DVRs (possibly not the HR34) are sluggish compared to the snappy interface of the 722s, but I think the DTV DVRs are more reliable.