I would wait. The guy selling the HS-U748 is crazy if he thinks he'll get the $200 he's asking. They pop up for $40 (about what I paid for mine), but you have to be patient. Remember, it sold for $700 new.
I think the AG-1980 is a little more desirable, especially for dubs, so it commands a bit more, but again, if you wait, it should have a more reasonably priced model, although the Mitsubishi by my experience will be cheaper.
Keep in mind the last of these good VCRs were built almost ten years ago and they weren't the common VCR you bought grandma so she could record Johnny Carson. They were made in far fewer numbers and they're what VHS enthusiasts seek out.