I went through pretty much what you're contemplating 20 years ago. Exactly 20 years ago, in fact. I had a large Canon FD system -- two old F1s, both with motor drives, and an FTb. FD Lenses from 20mm to 300mm, plus a Sigma 600mm mirror. And I had macro stuff -- the FD bellows, 50 and 100 macro lenses.
While I loved those old Canons and the FD lenses, I was kinda tweaked at Canon at the time for changing their lens mount. I gave it some serious thought and decided to change over to Nikon. The idea was to do it gradually, pick up good Nikon pieces as I could afford them, and slowly move over into autofocus. Fast forward a couple years and I had two large Nikon outfits -- an F2 and an F3, both motor driven -- with an even larger assortment of lenses than I had for my Canon system. All manual focus, though. I just didn't see the need anymore, especially since I was able to pick up used MF gear for quite a bit less than its AF equivalent.
But you know what? The quality of the photos I took with the Nikons was no better than those I took with my old Canons. And I found myself missing my old F1s. In the early 90s, I bought my wife an EOS Rebel, and gradually picked up a lens here and a flash there for it. After the Rebel wore out, I bought her a used Elan IIe, which came with another EOS lens. This past Christmas, she bought me a digital EOS XS with lens, and now I have almost as many EOS lenses as I do for my F2 (the F3 system got sold off during some lean times in the early 90s). So, here it is 20 years later, and I made the Canon MF to AF switch anyway without really thinking about it. I still miss my old F1s though.
I've enjoyed using my Nikon gear -- especially the F2 -- but I guess if I would have had to do it all over again, I would have just kept my FD system and expanded it instead of converting to Nikon, since I wound up going the EOS route rather than the Nikon AF route anyway.
Just a bit of perspective for ya.
Best,
Michael