I do not have a favourite brand however I always end up with an expensive one, so usually wait till there is a sale on them.
I do not, however, like latex foam as I find them too hot for our summer so it would be some type of inner spring, orthopedic one that I buy.
My wife and I went through multiple mattresses when we first got together. Firs, we got rid of my old mattress, it was really old and was ready to be replaced, then we got one from Sears that literally fell apart on less than a year. Next we picked up a cheap mattress at Costco which was okay, firm but not too firm. We had it for a couple of years but then our neighbour got a huge infestation of bed bugs which spread though-out our condo building. After multiple visits from pest control, we had to throw that mattress out, we couldn't get the smell of poison out of the mattress. Finally, we bought a foam mattress from IKEA, and we absolutely love it. It's the cheapest mattress we've ever owned and it is by far the most comfortable.