Rhino mount is cheapest. It works but has no bells and whistles. You can move up exponentially in both performance and price from the Rhino. The biggest issues people have with the rhino is no vertical adjustment and wobble where the J arm attaches to the mount.
I use a higher end mount that has vertical adjustment but also still retains use of the standard J arm. The wobble does not bother me as I am rarely if ever running around. Mounts are really tailored to what a customer needs. They can get very expensive for the designer stuff. Most mounts that use the standard J arm will have some wobble. The newer stuff such as the INVG still use a dovetail but do away with the standard J arm and is a much more stable mounting platform.
Mounts are one of those things that have infinite talking points and really boils down to what you can afford and what performance you need. You just need to get the job done fast and cheap ? Get a rhino. You get more features and better design as the price increases.