Athearn's newer run retooled RTR line is almost on the Genesis level. Athearn had many runs of RTR. (I will not mention genesis in the chronology)
The original RTR was a bluebox shell on a bluebox drive (with the arc welding light and not DCC ready) but with Celcon handrails, a more crisp paint job, nickle-silver wheels and pad-printed numberboards. (example - I don't remember any particular examples, but I have seen them)
When the hex drive came out, some models were still the original RTR with the new drive. (example - the first run of FURX SD40-2s)
They also had an in-between version where the grab irons are installed, but still retain the bluebox shell (but may or may not have the hex drive) (example - GP38-2s/40-s)
Athearn then came out with new retooled RTR locos. They had grab irons, see-through fans, and the hex drive, but still not DCC ready. (older runs of the SD40-2s)
When Athearn started putting light boards in their locos with a DCC plug, the engines were DCC ready, had the hex drive, and had microbulbs for front and rear headlights instead of the arc welding light. All engines after this "phase" have the hex drive.
Athearn then started producing locos with new tooling that they have aquired from buying out RailPower Products. The RailPower locos are nearly identical to the version before it except the numberboards aren't clear and can't be lit.
(When RailPower Products was in buisness, they produced shells that were more detailed than the bluebox ones and were designed to fit on the bluebox drive as an improvement on Athearn's shell)
Then there is the newer retooled SW1500s. They feature a new motor, have the handrails mounted either to the top of the walkway or the sill as appropriate for the prototype, and etched metal grilles.
NONE of the Athearn RTR engines have ditch lights. None except maybe for the latest run have MU hoses, air hoses, coupler cut bars, lift rings, etc. All Athearns require a bit of power to get it to start moving (on DCC, CV2 would need to be set to around 70 whereas an Atlas loco would have it between 10 and 20) All Athearn motors may have a chance of having that distinct Athearn growl (but it will run smooth nonetheless)