Once you move beyond basic setups, MRC gear usually comes into the picture pretty quickly when you're looking for power packs and controllers for sale. Their throttles and systems are what a lot of people rely on to get smoother speed control and more consistent operation.
Whether you're running DC or stepping into DCC with something like the Prodigy system, having solid control makes a noticeable difference in how a layout performs. You can find more in model trains when building out a complete setup.