I have both.
If you're looking for a headset that will take up less room in your flight bag, you'll need to find another case. It's the same size case as the Bose QC25 (hard shell). If you're looking for a lighter unit, it is a bit lighter than the A20, but the battery pack is a 2 AA battery unit, and is not light.
The A20 is easy to use and set up. Plug it in, find a suitable routing for the cable, stick it on your head and away you go.
The ProFlight is a shed load more fiddly. Getting the ear pieces in right is a bit more fiddly, especially if you want to maximise the noise cancelling. Also, getting the fit right is essential to not get discomfort over a long flight/day. There are different size ear pieces and it's worth spending time on it.
What is really neat with the Proflight is being able to tap the ANR off per ear. The ANR is pretty good but you do get more ambient sounds compared to the A20. Sound quality is excellent and my colleagues have had no issues with clashing etc.
It is a lot cooler to wear and a lot less interference with sunnies.
The Bose Proflight is an interesting option to the Bose A20. Is it better? No, in my honest opinion. Whilst the Proflight is lighter and cooler to wear, it is a lot fiddlier to put on and go, especially compared to the A20 (or any over the ear headset). Also, it will take up nearly as much room in your flight case given the size of the case. Sound quality is excellent, as it is with the A20.