You're going to get all sorts of answers from "it's the best" to "it's the worst."
We bought a Tiffin, honestly, more for the floorplan being exactly what we wanted. However, this coach continues to surprise me with how well it's put together vs every one of the 5 trailers and 5th wheels I've owned in the past.
I've also had to call the company for a thing or two and actually surprised I get answers fairly quickly.
Nothing is perfect, and I was also fortunate to buy from an owner who was meticulous. YMMV.
What Allegro Bay model are you looking at? I considered the 2004+ 34XB or the 37DB before we decided we really needed to stick with a bunkhouse. From what I saw, one can get a good value in the used Allegro Bay line. They had better features than the Open Road of those years but for some reason have depreciated to similar values.
I think I remember seeing in 2007 they went to 4 slides on the 37 model, changing it to 37QDB. For a traveling couple I thought that was a super layout, very big kitchen and living area.