There is some truth to the Ram transmission woes but that was an issue for the 2nd generation units, namely 1994 - 2002. Dodge had tried to convert their 45RFE series half ton transmission to work in the 2500 & up trucks with less than stellar results.
With the introduction of the 3rd generation platform, the 45 series transmission was put aside for the 545RFE 5-spd transmission. It was used in most of the light duty trucks until 2011 when the 65RFE transmission was introduced for the 1500 trucks and the 66RFE was introduced for the gas engined HD trucks. The 68RFE was developed in 2007 and has since been used in all 2500 & 3500 trucks with the Cummins diesel that aren't earmarked for the Aisin transmission.
I've towed either at TT or 5'vr using each of those transmissions. My '99 extended cab 1/2T with the 5.2L gas engine and 45RFE performed well and didn't have any problems. Of course, I was well under the GCVWR with the truck and trailer in combination.
My 2007 Ram MegaCab with the 5.7L gas engine and the 545RFE transmission initially towed the TT then we upgraded (and got heavier) with a 5'vr. Again, no issues with the truck or it's transmission over almost 140K miles. I respectfully take exception to the comments made about the MegaCab (or MegaCan as my grandson called it) as that extra room inside was great to have and I used it to the fullest. I still had plenty of bed space for my needs. Unfortunately, that MegaCan got smashed and I had to move on.
I currently own a 2014 Ram CC 2500 with the 6.4L gas engine (Yeah, I like the Hemi engine... got another rig in the garage with one in it
) and it features the 66RFE 6-spd transmission. It's a tow monster and, while I am not over the GCVWR of the truck with the current setup, I have no issues with the truck's performance pulling the grades here in the PNW. Before I purchased it I did look at all the offerings out there, gas & diesel, from GM to Ford to Ram and just liked the Ram's style and interior the best of them all.
If I had one thing to complain about it's fuel mileage but, heck, when I'm towing it's never gonna be close to Prius mileage now, is it...
Just FYI, I've owned the Duramax/Allison combination as well and, if I were to compare the offerings of Dodge and GM in 2003, I'd pick the GM combo again. It works well.
Today's trucks offer so much and, really, their capabilities are comparable and you can't go wrong with any of them, IMHO. Pick the unit you like and have a great time RV'ing out there!