If your budget will not allow for MiniDV, I would at least go with Digital-8. These two formats work with the "Firewire" or "iLink" digital interface to computers to allow editing of your videos, and they also both store the video in a digital format which is cleaner and has better resolution than Hi8.
Even if your current computer does not have editing capability, chances are you will have the camcorder, and especially the tapes you record, when you buy your next computer, and the one after that, so it would be nice to have the ability to edit your tapes at a later time.
Hi8 does allow longer recording times on a tape than the others; 120min vs 60min for Digital-8 and DV (at normal speed), so it is a little cheaper in the tape department.