Got a pigtail-plug for the 3+ and a used AHM4R for a couple of Jacksons. So, I have two shots at this. From the descriptions and discussions on the german sites the biggest change in the AHM4R is the larger current capacity for the lighting circuits and the inclusion of the automatic (retractable) ball hitch.

Just as an aside, for the retractable hitch there is a secondary module to be installed. A third module is for the trailer brake control. I spent the better part of an afternoon searching for information as it is rather dispersed. My ISTA version only has very limited info.

__________________
2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.