In other words, at the low end, you had scanners offering a maximum of 300 dpi, which was probably not adequate, up to 1,200 dpi, which is more than adequate. I've since learned that color scanning above 100 dpi is overkill anyway, but I do plan to use my scanner for documents and line art, which require higher resolution. Not all computers are capable of displaying that much range, but mine is, thanks to a high-speed graphics card I installed a few months ago. SCSI is usually faster, but it requires opening up the computer and inserting the card, and sometimes having to adjust jumpers and DIP switches to avoid those nasty hardware conflicts. I don't mind that so much, but it can be time-consuming, to say the least.
Parallel is slower, but it is much easier to do.
You just plug the device into the computer's parallel port, the same one the printer uses, and bang away. I was leaning toward SCSI because of the speed and because my printer already shares the parallel port with my Zip drive. I wasn't sure how many devices I could daisy chain on that parallel port. The only SCSI machine in my price range, however, was a 300-dpi in a damaged box, one that had probably been returned by another customer who had, perhaps, not been happy with it. That's when I started to think maybe I needed more research, and the tug of war began.