they are mostly all interchangable.... the hose ends are 1/2" NPS threads, and the shower head or hose can be replaced independently with a different quality if you choose to...
as for brands, they are mostly unbranded because they are sold by different distributors who may brand them as their own, but still identical to other "brands" of the same item... and there are different styles to choose from too.
RecPro and Valterra are probably the two most common names for the RV industry, with other names being used for the exact same model in the marine industry....