Some things to consider:
I had an older Honda riding mower (rear engine, not a tractor) and the motor was great. However the cut was sub-par, perhaps due the use of a large single blade.
If you end up with a walk behind/self-propelled mower, think about whether you'll be bagging much. If so, do yourself a favor and get a mower with a blade/brake so you don't have to pull start after each bag empty. If you're prone to back trouble the bending to remove/replace the bag then pulling the starter cord can really wear on you.
Currently I have a Craftsman 42-inch cut lawn tractor (with Kohler power) and Cub Cadet push mower (Kawasaki power). Both have been reliable, the engines have been great and the cut is fairly good. I had a Toro Recycler that was the best mulcher ever, but the motor wasn't so great (I must have got a lemon as a buddy had the same one and it never had trouble).