I upgraded from an EVGA GTX 980ti Gaming FTW ACX 2.0 to the EVGA GTX 980ti Hybrid last year.
The 980ti FTW ran the case a lot hotter so all the case fans had to ramp up quite a bit. At full load, temps were around 68-72 and fans were a bit audible over my head set.
The 980ti hybrid does idle a tad louder than my FTW but at full load all the heat goes to the rad and straight out the back of case and never went over 60 degrees. All the other case fans run at lower RPM, but at high RPM with the static pressure fan on the radiator the air pushing through the rad is audible.
Overall at idle the AIO is barely louder than my whisper quiet FTW. At full load the AIO is significantly quieter than the FTW.
I recently replaced all my case fans and the 980ti radiator fan with the Corsair Maglev fans. So now I can run the rad fan at 1500 RPM and dammitt at full load I can barely hear any fan noise over my head set and GPU temps never exceed 56 degrees.
I would still recommend air cooled GPUs if your looking to save money, the moderate increased fan noise at full load isn't a big deal, and you plan on keeping your GPU for over 3 years.
But for me personally I'm never going back to air cooled GPUs. The reduction in noise is a huge plus since my case is about 17 inches away from my head. My games will never freeze up over an overhead GPU, all my games comfortably run on max settings, there's never going to be any throttling, and the AIO GPUs are very slim so they don't interfere with the other PCIe slots. AIO warranty is only 3 years so this is only good for idiots like me that buys a new GPU every two years.