At least with the sidewinder, you can use dry or liquid media. It has become an expensive tumbler, but I purchased mine in 1985, when it was $119.00. I thought that was expensive then. I have replaced the container once. That used to be $45 but has since increased also.
I also have the Lyman 2200, but the RCBS does a better job of polishing the brass, IMO. I don't know if it's worth the extra $200, but I wouldn't be without it.