I don't have an opinion on which is better, never tried a rear conversion. But here is some food for thought.
1) You may need a different master cylinder to take advantage of the disc braking.
2) You may need to add a proportioning valve to ballance front and rear brakes. (More work to install, more to break.)
3) Your rear ABS (As little as it does on these trucks.) would have to be deleted and the light disconnected so it does not trip or set a light.
4) You maybe are pushing your wheels inboard or outboard with a kit or different axle. Likely not an issue if you have stock wheels and tires. But if you have big tires and rims that are close to the fenders that may mean more alterations. Or having to buy new rims with a different offset.
5) Unkown is how they will handle when towing a trailer? Will they be more likely to lock up and cause a slide or a jackknife situation. I have not heard folks complain these trucks won't slow down, skid easily, or jacknife. So what does altering the rear to disc do to the characteristics of the truck when towing?????
I think it also comes down to what you tow and your trailer. If your trailer has good trailer brakes your drum brakes should be just fine. In my opinion drum brakes handle more long hard braking (Down a grade) and handle heat better than disc's do. Also our rear brakes only do say 25-30% of the braking (To avoid skidding.) When you brake the nose and wheels get pushed down and track harder, the rear wheels unweight and loose some traction, thus why they are set to do less. So if you get say 20% more braking on a rear axle with disc, in theory are only getting a overall 5-8% increase on the rear axle. (Because your truck does not use the rear brakes to do 50% of the braking. Results may vary by make and model.)
So I would think if your issue is your trailer is making it hard to stop comfortably. Perhaps it more prudent to add brakes on the second (Perhaps the third) axle of the trailer (Double/Tripple its stopping power.) VS doing a big disc brake upgrade on your rear axle? So instead of making the truck work harder, let the trailer work harder to slow itself down.
Remember jackniffing and trailer sway is often due to the tow vehicle slowing down too fast, in a sense getting in the way of the trailer so it wants to find a new direction to travel. Then the trailer in poor tire conditions may find it easier to push out and around the tow vehicle rather than stop behind it.
Many forget the best way to get out of a trailer sway or beginning of a jacknife is to apply the trailer brakes evenly. (Only the trailer brakes. Not jam them on but apply them fairly quickly. When this happens it sucks to have surge brakes!) So if your trailer is working harder to slow, thus in a sense working to also slow the tow vehicle, it will stay straight in line with the tow vehicle. If the trailer starts to skid, the tow vehicle in a sense is trying to stop the trailer (While it is skidding.) the forward momentum of the trailer will begin to start a jacknife via a circular curve to the left or right to get around the tow vehicle. At some point you can no longer correct and have to ride it out.
Now if your truck had drum front brakes for lots of reasons I would say yes do the front conversion to disc. (You get most of the bennifit of improved stopping power of disc's, your vehicle is much more likely not to pull left or right when braking, no brake adjustments periodically, less likely for a brake lock up in a turn with rain/snow/sleet, etc.) So the pain of doing so, well out weighs the work.
