Stew,
Unless I'm mistaken, I think a third unit that is also marketed as a 'solar 30' is the unit offered by Renogy? It's generally more expensive, but no idea if one is better than the other? I have asked this question, myself, more than once.
You would think there would be some sort of control put in place, regarding marketing different products under the same name? But then again, calling a marine hybrid battery a "deep cycle" is but one example of marketeering gone wild.
The unit you have seems to be a combination of at least two other units... it has oval buttons, but has the one piece (allegedly better) back plate. So maybe that makes for 4 different units all being marketed as a 'solar 30'?