I have 17 Rivarossi engines mainly bigboys and mallets and a few cabforwards I think there's a hudson in there some where as well. The old stuff is just that "Old Stuff" if you want a cool looking engine to sit on a siding or in your engine terminal then and old AHM is just fine. Problmes with them are many. A: Old style 3 pole motors are noisey as an old coffee grinder and produce no where near enough power. B: It's virtually impossible to get parts for them. To my knowledge there is only one guy in the country who has a decent stock of Rivarossi part. Gulf Manor Hobbies in Ohio. All I'm gonna say is good luck.
The new Hornby Rivarossi's are head and sholders above the old stuff. Can motors, better gearing, quiter running gear, extremely better low end speed control and I feel much better detail. I have upgraded most of my old stuff with can motors. It can be done and no it's not an easy retro fit. I have used many different motors etc. so I have no one set preference. I got tired of spending a lot of money for somethign I could do myself.
In short if you want a big monster to run on your pike and don't have a lot of money (like any of us do) Then the Bigboy isn't a bad choice. How ever if you want to run a big articulated and it doesn't have to be a Bigboy then you have a lot of better choices in my O/P.
Cabforward: Intermountain makes a beautiful runing as well as looking cabforward. DC or DCC if you want to run a nice big articulated you get the most bang for your buck with a Proto Heritage 2000 2-8-8-2. I have 2 of these now and plan on running one more eventually. The detail is fantastic, the overall qualitiy is as clsoe as you'll get to a nice brass import in plastic, parts are readily available, they run absolutley fantasitc either slow speed or pulling a 30 or 40 car coal drag.
I have so many RR's becasue way back when it was either that or brass. There is not one of my original Rivarossi's that I paid more then $50 for. Why would you want to pay some guy at a train show $200 for an old clunker that has been sitting in abox some where when you can buy a new one from Micromark for another couple of bucks. I got tow of my new ones from them for some where betweet $200 & $250.
Just my 2 cents worth, I spent the rest on trains.
If you choked a Smurf what color would he turn?