Here’s my HO 4-6-2 knowledge, not counting custom brass or any K4s:
Varney - Freelanced diecast and brass kit, but very old and expensive due to rarity.
Athearn - Generic heavy, mostly plastic construction, decent detail for their day. Late productions had all plastic drive wheels (including the flanges), and the chassis isn’t what I would call great. Expensive due to rarity.
Mantua/Tyco - USRA-ish heavy, all metal construction for early ones or plastic cab and tender body for later ones. Usually sold as a kit, smooth running (usually after some clean-up and tuning since they’re old) and reliable.
AHM/Life-Like/IHC - USRA Light, basic model by Mehano, molded on railings and not very heavy. Decent runners, but the motors have no low speed control.
IHC Premiere - Same Mehano model but with separate railings, skewed armature motor and a flywheel. Smoother runner and better looking than the earlier version.
IHC Premiere Gold - Same as Premiere but with RP-25 flanges, blackened railings, DCC socket and better paint.
Bowser - USRA light, all metal kit with Cary boiler and brass details. Lasts basically forever when built correctly and has almost zero cast on details, but they’re hard to find and take time to build. Cab is somewhat freelanced.
DJH - USRA light, all metal kit made from white metal and etched brass. Includes NWSL or DJH gearbox and a Mashima motor. Detail is decent but has a lot of cast on piping, and Mashima motor choice is a little slow and weak, but they look nice and run great if built correctly.
AHM/Rivarossi - USRA heavy, mostly plastic and have large flanges and a cab mounted motor. Runs nicely with some tuning, and the molded details are sharp.
Rivarossi - Upgraded with RP-25 flanges and a boiler mounted can motor as well as blackened metal details, but kind of hard to find. Very smooth running.
Athearn Genesis - USRA light, very nic