My experience has been that the video quality of the DVDs is so far superior to the MPI VHS tapes (and even more so when compared to my home-taped VHS cassettes from Sci-Fi) that I prefer to buy on DVD all the shows I previously owned on VHS. Of course, knowing that eventually the entire series would be on DVD, quite awhile back I sold all of my MPI VHS tapes (volumes 93-200) on eBay to various people who felt strongly enough about buying those tapes at about $2.00 each (when they were still around $10.00 each at MPI). I took a loss dollar-wise, but that doesn't matter to me. (I destroyed the earlier episodes that I had taped from Sci-Fi, since selling those would not have been legal.)
Since you have a combo player, you might want to buy a DVD with some of the same episodes you have on VHS, and then play an episode or two side by side, switching back and forth between formats to view the difference for yourself. That might help you make a decision.
Good luck!
Brian