For me it is CRC, excellent cleaner and easy to use. Be sure you purchase the "safe for plastics"
I use the Centerline Products car with the weighted roller. Soak the roller and let her rip. Walk ahead and keep the roller soaked. CDC evaporates quickly. I clean the track twice per year and I pull my rolling stock behind the engine. Lots of gop gets attached to your trucks and this cleans them sparkling clean. In addition I fold a paper towel and spray with CRC then wipe the tracks off.