I'm curious to know what your opinions/thoughts are about the various brands of pianos you've played, which is your favorite, and why?
You've asked a question that is surprisingly difficult to answer! Every instrument is different, let alone every brand. Every time I make a generalization about a maker, I find a piano that shatters my opinion. Usually Kawai pianos tend to be dull and weak, but once I played a concerto on a glorious Kawai with great projection and a beautiful tone. I love Steinway pianos, but I'm frequently forced to play Steinway pianos that are out-of-tune, out-of-shape, and unregulated - that's no fun.
By and large, Steinway makes the most satisfying instruments that I come across. They generally have the largest spectrum of tonal and color possibilities, the best dynamic range and projection, and the most consistent action. They also last forever. Mason & Hamlin, Boesendorfer, and Faziolli make terrific pianos as well. Yamaha pianos generally have a bright sound that is fantastic for some pieces and not for others.
Perhaps I'll update this response after I ponder it a bit more.