Thanks you all for your answers !
All of these devices look very similar; (even in colour). So either the Chinese share a common design or they come out of the same Chinese plant...
I am attracted by the plywood stand, alas I can't store it in the garage. On the other hand, I can store the hydraulic lift under the workbench saving premium space for both motorcycles... Thanks for this wonderful idea ! (sometimes, I need to put the car in the garage for oil change or minor repair, so getting the bikes out is enough trouble. If I have to empty the garage before attempting work on the car, I will get a little upset by this rolling couch...)
I will try to see one in my neighbourhood before buying.
Thanks again !