I have a 12" (non-sliding) Rigid and a 7-1/4" (non-sliding) Ryobi. You have a Rigid, so are familiar with the brand. Personally I'd happily buy another.
The Ryobi is a nice little saw, I put a non-ferrous blade on it and use it to cut brass and aluminum. I have a handful of Ryobi tools and they do their jobs fine, but all are used for fairly light work.
Sliders add another element for misalignment, so I can certainly see Fbmoose's point that quality on the lower priced saws may be more noticeable compared to non-sliding saws.
I've also noticed there is far less available in the 10" size. You may not need a 12" but you might want to consider that simply to have more options. The price of the blades was surprisingly not that much more.
I saw in the other miter saw thread you are making cutting boards. Do you have a table saw? If not you might consider that vs buying another miter saw, similar price range to a sliding type miter and it opens up a lot more options.