Pat, true, this is one of those subjects you're going to find different camps and different opinions.
Sliding miters have largely replaced the radial arm. Its also a reason why not many are made anymore. If you check the major machine companies, I'm pretty sure you won't find a RAS carried by any of them. That said, the "old iron" saws or the good ones like Red has are very good saws but also very hard to come by and often as expensive as a quality slider.
The issues with the homeowner type RAS's are accuracy, holding settings, and power. You definitely have to keep a sharp blade on them, as well as the proper type blade.
Yes, they can be bought for next to nothing, but frankly that's about what they are worth. That said, it does have a place in my shop, as I'll explain. I've owned a Craftsman (sorry but a real POJ IMO) and an old iron DeWalt 9" which was a great saw, but unfortunately the motor died. My current saw is a Rigid - not much better than a C'man.
I also have a miter saw (non slider). In my shop, 90% of RAS use is rough cross cutting dimensional lumber (boards), period. I am not that concerned about maintaining exactly 90, but I will say this is the biggest issue with the common homeowner type RAS's (again, with the exception of the old iron like Red's). One bump on the arm and you're in for a realignment session. They also seem to mysteriously loose their setting just from normal use, so plan on doing an alignment check at least every few months.
In my shop, the miter saw for is the "go to" for cutting miters, especially to an exact angle (try dialing in 22.5 on a RAS). Again, unless you're dealing with a high caliber RAS, if you do cut a miter, you'll have to check/reset for 90 every time you change it. This puts a cramp on the work flow.
So this is why I would advocate passing on a RAS and go with a slider, and you'll probably never see a need for a RAS.