I usually buy by the model and roadname rather than brand, but Williams caught my attention when they started making scale GG1'S. I have the 4935, and it can pull 5 of the 20-inch aluminum cars at speed so high I have to be careful not to derail it on 054 curves.
I also bought the trainmaster because I wanted CNJ, and it cost about one fifth of an original Lionel. It pulls four scale Madison's as fast as the GG1.
I have th F7 AB set, and the Alco PA, both PRR, and the postwar K4. I am looking to convert the K4 to DCC, as I found a sound system recorded from the 1361.
I have a USRA Mikado, and it can handle 15 scale freight cars at 2/3 full throttle.