Walthers Trainline, Mainline

What are the differences in the Walthers Trainline and Walthers Mainline locos? I have a Trainline GP9m and I’m just wondering how it differs from the Mainline line. I’m just interested in the difference in mechanics, not electronics or details. I know the Trainline locos are bereft of details.

It looks like the Mainline locos are going to be the old P2K 1000 and the Roco SW-1.

http://www.internettrains.com/

Go to the Walthers Mainline section.

Click on the individual locos for power train descriptions.

The helical cut gears would be a good thing in consisting. I wish my F units had them.

Off-topic, but I wish they would sell the DCC version as a seperate item. It may not be too prototypical, but it’s the only RTR low nose GP9 out there at the moment.