I used to have like 10 TiVos, but I sold a few to WeaKnees, as well donated a few. I decided to simplify to just 2 DVRs when the Premiere went off support. I really don't have a lot of TVs, and streaming is getting to be decent now.
So my main DVR is a Roamio, and my backup DVR (with secondary TV) is an Edge OTA. The Roamio is way better. Roamio can do antenna or cable, has 4 tuners, can fit a full size hard drive, or run off a quiet, fast, and slim SSD (what I run it with). Edge can only run a notebook hard drive (2.5''), has just 2 tuners for antenna, and you gotta choose whether you get cable or antenna capable. The only thing good about the Edge, is that it has a nice design somewhat similar to the slim Sony PS2. Okay, so it also has a slightly faster processor, so 2 things.
Roamio is better, except for the curvy design, but still better than the wonky shape of the Bolt.