You will get lots of opinions, and I wish you good luck in sorting it all out when the thread dies off.
I own the following, and would rate them as follows: (all HO)
PCM 2-8-8-2 Y6b - heavy (metal), solid runner, excellent detail...rates 4.5 stars. Why not 5/5? It has a quirky tether connection between the tender and receptacle below the cab.
BLI Niagara 4-8-4, K4s 4-6-2 (metal), J1 2-10-4, J1 Hudson 4-6-4, and a Duplex T1 4-4-4-4. Each of them is excellent. Not top drawer on details, but darned nice, and they pull fairly well. The Niagara and K4s, believe it or not, have equal capability in traction. The mighty J1 and Duplex are strong pullers. Each of the four runs well, reliably, and they look and sound quite good. 4/5 across the board.
Rivarossi H-8 2-6-6-6. It is superbly detailed, and a huge engine. The tender is very light, but it doesn't seem to be an issue. It came with incorrect sound files on the otherwise very nice LokSound decoder. It was easier to replace the decoder with a Tsunami. I wouldn't rate this engine, yet, as a strong enough puller for its size. All in all, it gets 3.7/5. I hope to warm up to it.
Trix metal Mikado 2-8-2. This is a very nice little engine, but a little light. Detailing is quite good. I had the LokSound yanked, once again, because it was the early version with its limitations. Tsunami medium to the rescue once again. I would rate this engine as a 3.6/5, down from perhaps 3.9 because of its light traction.
Like Like Proto 2000 Heritage Series switcher 0-6-0. I got it DC, so it has a Tsunami light in it. It rates up there with the Rivarossi in terms of details. It is a very nice tiny engine to look at. It rides well, but it is light, as you would anticipate. Strictly for yard shunting, although it can shove four Walthers heavyweights and a reefer without trouble in the yard. For what it is meant to represent, this engine rates 4.5/5. I would urge you to get its bigger brother, the 0-8-0 for yard work. If you can get a deal on sound equipped engines, get two.
Lionel Challenger 4-6-6-4 (metal). Another solid, heavy engine that runs really well. It pulls a ton. It is light on details, all things considered. I would rate it overall at 3.9/5.
That is my stable of steamers. I have a new Bachmann Spectrum J Class 4-8-4 that I got for a song from M. B. Klein's a few weeks ago. I have a heavy Tsunami in it. I have not been able to give it a reasonable test due to running problems. It seems to be a nice engine, but it stumbles, or lurches at slow speeds, and occasionally would simply chuff like mad without turning a wheel.
It is back with my decoder installer who reports that it is now working well. I haven't talked with him about the details. I would tentatively give this engine a 3/5, feeling magnanimous. If it turns out to be repaired, I will probably settle on 3.5/5. The side rods are very light in colour, too new...they should have been blackened a bit. The bad running gear rankles, to be honest, and has left the new experience soured a bit. I hope it can win me over in the coming weeks.
-Crandell