What is the difference between these and the OEM ORP ATW3A's?
Not much really. The A/T3WA is basically the the AT Trail sold as an Original Equipment tire for the Ram 1500, and Mercedes G-Class.
Falken doesn't list any specs on the A/T3WA, but they do for the AT trail which is rated the same on all aspects as the Rubitrek. The key difference being that it has additional values given for comfort and fuel efficiency, which suggests they had to have those results to be used as an OEM part. Purely speculation though.
At the end of the day, they're pretty much the same tire with a different name as far as I can tell.
The OEM AT3wA and the Rubitreks share similar tread design than that of the aftermarket/off-the-shelf AT3w. AT Trail should not be considered for full size trucks as they are geared towards crossovers, SUVs, or compact trucks, even though they look similar in tread design.
The OEM AT3wA has to meet certain criteria limits for noise, comfort, handling, MPG (among others) in order to be equipped on vehicles from the factory. As such, the tread design is revise to meet those thresholds. The Rubitreks has a more aggresive shoulder rib in comparison to the AT3wA. This can play a part in additional noise than the AT3wA but technically should be quieter than the regular AT3w (with the entire tread being considered). I do have to point out a key factor with considering the Rubitreks.
The Rubitreks are not sold by every vendor and as such, must be kept in mind prior to purchase. If you are local to your tire seller or this seller has multiple stores wherever you travel to, then the Rubitreks can your choice tire, breaking away from the Wildpeaks in the area. However, if you happen to live where they are not locally available and you need a replacement right away, it would be best to stick with the Wildpeak AT3w as those will be more accessible than the Rubitreks.