Has anyone used a RedArc TowPro while towing over steep grades?

[BrianDenver]

I switched from a Tekonsha brake controller to a RedArc. I noticed it has two modes; proportional and user controlled. The examples given by RedArc place the user controlled functions in an off-road scenario. But it also sounds like user controlled operates similar to how the Tekonsha did by following the brake lights. From what I understand, proportional detects inertia instead of the brake lights - is this actually better?

Have you noticed any difference in operation of either mode?
Any use in the mountains in either mode and can tell me which may be preferred?

Thanks in advance!