Both systems are awful and if you got that far without problems you are definitely in the minority. I can assure you it does NOT get too much hate. I was a GM engineer for a little over a decade and was around when the AFM stuff first got implemented. If anything, it doesn't get enough hate. Stupid idea that doesn't even really work and causes all sorts of problems. I'm glad you have been lucky, but don't start thinking they all will be trouble free.

Well, from what I understand for 2019 MY they offered DFM in the Chevrolet 1500/GMC Sierra 1500 with the 5.3L and 6.2L V8’s, but only on the 5.3L L84 (while L82 retained AFM) and 6.2L L87.  Both technologies are bad, and I would recommend disabling them after buying the truck (but the hardware is still intact).  The real solution is to remove the hardware and re-tune ECU but that is thousands of dollars and will definitely void any powertrain warranty claims.  Anyhow, we have some excellent articles and videos on AFM and DFM under our Cylinder Deactivation sticky so I would check that out, but between the two I would say AFM is better because before you only had 2 modes:  V8 or V4.  Now, with DFM you can have up to 17 modes (that includes operating on 2 cylinders only).   Each cylinder has the cylinder deactivation hardware, so 2x what it was before (under AFM).  There is more potential for issues, esp. if you are not on top of your oil changes (clean oil and correct viscosity are very important here).  But I also don’t trust the quality control to be in place (esp. from their suppliers), so all that hardware is a liability.  Cylinder deactivation is one of the stupidest things automakers are implementing:  all that additional complexity not worth it.

I would hope that since DFM is the second generation, they would have squashed some of the bugs from AFM.

Did you check the FAQ?

AFM and DFM is about as stupid as auto start/stop.  The road to Hell is paved with good intentions!