I have never tried AOS 4.x. I still actively use 3.9 on classic hardware and MOS 3.6 on a powerbook.
Still have 3.9 setup on my A1200, hacked to death with software patches and hardware mods. Still has a switching issue with RTG/WHDLoad I can't fix.
It's amazingly quick can run most summvm games fine and it's a pretty good machine for internet browsing.
I haven't touched it in awhile, but can't bring myself to sell it.
Feels just like my OS4.1 update 6 setup, however not as fast as the peg II.
Everything on os4.1 is in the same place as 3.9. So I get the 3.9 experience (with modern additions) but it's far more stable/faster. Plus I felt at home on first boot, just like running afaos/zune on 3.9.
I agree if "one banner" was working together instead of red/blue it would have helped, particularly in the software application area which is the biggest void of all flavors of Amiga.
There was a time when there was more more bickering than progress, if we can all focus on one goal imagine the list of apps we could have now :-)
Welcome to MOS...
Thanks :-)