What locomotive brand do you like the best. As for HO scale I’ve owned Life Like, Bachmann, AHM, TYCO and Athearn. Athearn tops the list for me in HO. I know there are better locos out there but I’ve never tried on.
In N scale KATO is by far the best. I’ve had good running Atlas & ConCor, and some not so good running cheaper brands but I can honestly say that KATO is the smoothest I’ve ever used.
My experiance has always been with DC locomotives, so maybe some of the newer stuff is different.