I used to sell camaras. The professionals usually had two Nikons, because one was always in the shop. I switched from Nikon to Olympus and never looked back.
I have a few OM-1/OM-2 bodies. I much prefer the Olympus to the Canon and Nikon for a variety of reasons, the compact size being a primary one.
Shutter speed is conveniently located at the front of the body, coaxial with the lens (vs. on the top of the body), and overall, a very convenient system to manipulate.
The biggest drawback, which is not much of one now, is that OM mount and Zuiko lenses in particular were expensive.
Between the OM-1 and OM-2, I prefer the OM-1 because the shutter is all manual. I sometimes shoot in cold weather, batteries lose juice when cold, and it's maddening to lose a shot because the battery-powered shutter won't fire.
I'm certain there are examples both pro and con, as many as there are people using them. I also know many great pictures come from other brands. Nor am I a professional photographer, although I do use and buy some pictures.
Still, the majority of professional photographers I've met use and prefer Nikon. There are a number of ways to go. I would still suggest lowest price unless there are other reasons to buy high. If the person is just now taking photography, by the time he or she is out using it digital will have even more choices and alternatives. You wouldn't believe how many camera stores are history in Denver now. The only remaining ones seem to be the larger retailers and the better used stores, who have a following and good service departments. The large stores have added free classes for buyers to help them learn photography, and helps build customer loyalty.
I'm with you on the Olys, mine are usually covered with frog spit and bird poop, but they just keep on shooting.