Sir, there was a several articles about RRS+Towing issue due to short wheelbase there seems to be stability issues and Full Size RR is much better suited vehicle in that retrospect.
I understand that you are not at the point of choosing which one buy to but have these already, just wanted to let you know that people made number of complains in this regard. May be google it, do some research.
4.4L has plenty of power for towing. I've towed for many years a motorcycle trailer (800 lbs) plus a motorcycle (550 lbs). Up and down mountains, no sweat at all. You barely know the trailer is there....tons of power from the RRS. I should imagine you'll have no trouble with either engine choice.
I'm running a 2017 Diesel FFRR now, same story, plenty of torque, power...towing a trailer hardly makes these vehicles break a sweat.
i tow a ~2200 lb boat once a week or so with my 4.4 - no issues at all - barely feel the load at any speed. even going up and down hills, the engine has enough grunt to power through it. the suspension leveling itself to compensate for the load is a nice touch.