Although I've never had an OM1 I've had an OM2n for about 30 years. I've also had an R8 (and R9) for about 15.
If it's ONLY the handling that you dislike about the OM then the R8/9 will probably be nicer to use. It's a larger camera and ergonomically very well designed. It has it's own issues however, some can scratch the film (but this can be repaired), and maybe there have been other issues with them, you'll need to do more research. I've had to have a couple of things repaired on my R8 but in functional terms I've always been very happy with my R8/9 bodies.
The metering on the R8/9 is quite good too and you can switch without moving your eye from the viewfinder which I always found nice.
One of the brilliant things about the R8/9 is the viewfinder which is quite similar to the OM's. The R8/9 is very easy to focus accurately and is very bright. It's still not as high magnification as the OM, but it's very good.
I do think the R8/9 is one of the best SLR's I've ever used, although I prefer the Canon 1V only for it's more accurate spot meter.
In terms of the lenses, don't worry about it. Zuiko has as many gems as Leica although it depends on your specific needs and budget. Fore example, I have the Zuiko 28/2 (also the Zuiko 28 f2.8 and f3.5) and the stunning Leica Elmarit-R 28/2.8 E55 and although the Leica R is technically the better, sharper lens I far prefer to use the Zuiko 28/2 for it's character and sharpness wide open. The Zuiko 28/3.5 Zuiko is amazingly sharp for a lens worth about $50! Same could be said of most Zuiko 50's. The Zuiko 50/1.4 is an excellent lens and I find myself using it more than the Leica Summicron-R 50/2. Having said that, some of the Leica R lenses are absolute gems and I've always loved the Leica Summilux-R 80/1.4 and the Leica Sumilux-R 35/1.4 which are both very easy to focus accurately on the R8/9. The relatively cheap Leica Elmarit-R 24/2.8 is also a very nice lens and one I've always loved using but TBH, I prefer the Zuiko 28/2. Then there are special lenses in both camps and if you prefer macro work then the Zuiko's might be a better choice, but fast teles are arguably Leica's forte. My favourite is the APO-Summicron-R 180/2.0 which is a dream to use on the R8/9, but obviously this is not a cheap lens.
The biggest mistake people make when moving to Leica R (or even M but to a lesser degree) is that they don't do their home work and learn what the various lenses are and their differences. For example, many people will buy an early (from the 70's) R lens and find it potentially mediocre in it's performance whilst there might be later version of that lens which might be the state of the art for that focal length. The Elmarit-R 28/2.8 E55 is an example of that. The latest version, denoted by the E55 filter, is a much better lens than the early R 28, and is much more expensive. The same applies to various 180', 90's, and various other R lenses. In general, the latest R designs are the most expensive and optically the best of the R line.
The Leica R4 is actually also a very nice camera however there are issues with these and possibly best avoided. I have an R4 with a current/latest focusing screen fitted and I find this better for wide angle lenses than the R8/9. The standard R4 focusing screen is at least 1 stop darker than the later R6/7 screens which also fit the R4. However finding a decent R4, much less a current focusing screen, can be difficult.