NWSL and Jay-Bee are both good. I also got a replacement set of loco wheels and gears from Atlas, and they were good too. Now days, almost any good manufacturers wheel sets are good if they are nickel silver. The trick is getting the axle the correct size so it fits the gear without cracking it.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.