The 811 use to be able to get HD from Dish. This is back when it was MPEG2 QPSK and it was 5 channels for 10 bucks. It was HDNet, HD Theatre, TNT, ESPN and I **think** Discovery.
That is why there are all those outputs.
When Dish dropped that package the receiver became a elaborate 311 with the option to get OTA HD.
But as noted there are issues with the 811 (and now as the 381). The big one I remember is if you were on a OTA channel too long the receiver would freak out when you switched back to satellite. You had to redownload the guide
I guess if you REALLY want to use a DVI or component cables to watch 480i programming yeah then the 381 is for you. But I've worked with 311's for years now (and before that the 301...only difference is the 311 can do 8PSK and the 301 cannot) and have had no issues with those