It looks like all of those companies do a custom build process and that's why they are very expensive. The myron & davis units are fully motorized which is why they have the topload slot... but they are also very high quality.
I've never used the audiovox units but it looks like a similar process (custom build to match). The thing that concerns me about them is the "1 touch opening" which I think means you push the button to pop the screen and place the DVD on the spindle yourself... that setup is usually more prone to vibration problems (though I can't say it's "bad" from first hand experience).
Never have dealt with the Rosen at all though it looked a little more full featured with the USB inteface.