I've got a Rolleicord III (Xenar lens, similar to the Tessar-type Rokkor on the Autocord) and a Rolleiflex 2.8C (Planar) and have done some casual comparing of the two. (Actually, I've got an Autocord as well, but the focus lever has fallen apart and I need to fix it someday.) The results basically are that (1) the Rolleicord has really good optics; and (2) the Rolleiflex has even better optics: sharper, contrastier, less vignetting when wide open and more subjective "pop". I'd expect to see the same relation between the 'flex and an Autocord.
I don't think the optical difference justifies the price difference, on purely optical grounds and as a hobbyist user. (Someone who was more dependent on exquisite optical quality would naturally feel otherwise, and I'm intentionally neglecting the general "feels right" vibe of the 'flex and other non-optical considerations.)
I've never heard of a reasonable person being disappointed in the quality of an Autocord (except for that focussing lever).
I have a Rolleicord IVa and have really enjoyed shooting with it, but I enjoyed it even more after having the viewing screen replaced with a Maxwell screen. You will find many diverse opinions about this, but I think the older Rollei TLRs with factory viewfinders were rather dim.