I've never owned an Olympus, but I've owned two F2AS/MD2 camera bodies and two F3/MD4 bodies. They were fantastic cameras. As others have stated, the Nikon professional cameras are built to last. The F3 had a production run from 1980-2001, and outlived the F4 by five years! I was shooting a playoff football game in 1981 when the temperature was in the single digits. There were about seven of us on the sidelines with almost every major make of camera out there: Nikon, Canon, Pentax, Olympus, and Minolta. All but two of the cameras quit working because it was so cold. The ones that didn't miss a shot: my Nikon F3/MD4 and another friend's Nikon F2SB.
The F3 also has an electronic shutter that was at the time the most accurate of all 35 mm cameras, and I've seen independent lab tests confirm that, including comparisons with Leicas costing three times as much! Of course you know that when shooting film, you never REALLY know what you shot until the film is developed. That consistent reliability is what kept the F3 in production for over two decades. The F3 also has virtually 100%, full frame coverage in the viewfinder, while the OM-1 covers about 97%. The built in light meter uses a centered-weighted 80% reading that yields more accurate results that are much less affected by stray light. The MD4 motor drive is also faster than the Motor 1 or 2 that Olympus used, 6 fps (mirror locked) or 5.5 fps for the Nikon vs 5 fps for the Olympus. That difference may sound irrelevant until you shoot something like gymnastics. (I'm assuming that you have an Olympus OM-1MD or OM-1n.) The Nicad batteries in the MD4 are good for over 60 rolls whereas the Olympus is rated at 40. I don't know about the Olympus, but the Nikon has the feature of powering the F3 with the motor drive (not so with the F2/MD2), so no need to worry if the battery in the camera goes dead.
I also owned the 105 f/1.8 and it is a fantastic lens.
All of these extras may be beyond your needs, but if you decide to step out of the studio, the Nikon F3 offers many advantages that Olympus doesn't. One of my biggest regrets is selling my first F3 back in 1984.