I did have the FM2 and FE cameras because they were part of the system I was using. Mostly back-ups for the F4/F5.
I've always thought the OM4T was the greatest camera Olympus ever made and is much more camera than the Nikon's.
If I was picking in this day and age I would go with the OM4T. Great spot metering, great construction, well thought out system.
The only advantage of the Nikon's is the availability of used items and lenses. Some of the exotic Olympus lenses are very hard to find. I remember seeing a 180 f2 at a news photographers trade show years ago, but have never seen one come up on ebay. Not that I'm watching every day.
If it was my money I would go with the OM4t.