Also look at the WolfPup 16FQ (we have the 2020 model and the new 2021 model has almost the exact same interior as the Black Label).
The main reason I prefer the 16FQ is that the murphy style bed allows you to get in and out without having to climb over the other person. The bathroom is also bigger and has a big sink. The 16FQ's outside mini fridge is awesome!
We don't have a Black Label so I can't comment on the airflow but the frameless windows look nice but they can shatter easier from rocks hitting the side than the normal windows.
We don't have a slide either but putting the bed up create a good amount of space. Also, slides adds weight and another thing that can break. Depending on the model, the slide may also prevent you from accessing the bathroom or fridge if the slide is closed.
50W solar is somewhat of a gimmick. It can charge the battery so you can run the lights, fan, awning etc. The AC, microwave and TV will not run on the battery since these units do not come with an inverter. The fridge will run off 12V but with the standard size battery it will kill the battery in less than a day.
To go off grid with Solar you need about 300W and an inverter. A generator would be a better option for boondocking in a WolfPup especially considering the fridge does not run on propane.
I think the warranty on new units are more important than used units simply because any major issues during manufacturing would have been found and fixed. We did not get an extended warranty because of the high cost and if you are handy you can order parts from your dealer. The glass cover of our stove shattered and it was only $128 total to replace and the warranty would probably have not covered it because it was totally my fault.
The negatives with the WolfPups are that they have a single axel, have 3 small tanks (23 gallons), the AC is LOUD, no oven, the walls are not well insulated, not a lot of outside storage, cheap materials and a very crappy factory mattress (adding a mattress pad helps).
We love our 16FQ and spent 55 nights camping in it last year