All for lending a helping hand but I have no idea what adverts you’re talking about. It might help to at least post up some links or images of the ads in question.
What are peoples perceptions of them as brands?
My perception is that assos have positioned themselves at the premium end of the market at the expense of all else whereas endura try and maintain a presence across a wide range of budgets and cycling disciplines.
Quality of kit?
Endura, some good some not so, utilitarian and workmanlike. Assos, very high quality throughout the range.
Do people have brand loyalty?
When I’m buying something new I will always look first at the ranges from companies that I’ve had good experience of in the past. So I suppose that would count as brand loyalty.
I think you need to put a bit more thought into your questions. Surely the experience, type of riding, disposable income, brand availability and many other factors would all influence whether someone would consider buying one brand over the other. These questions seem vague and a little simplistic.