Why waste money when you can have everything for free and 3.1 runs better? 3.9 isnt even up to date but you have to download boing backs and updates from Aminet if you wish to use latest versions.
I used OS3.1, 3.5 and 3.9. Sure 3.5 was a half way but after installing 3.9 (with both boing bags) I never looked back again. And no, OS3.9 is not slower than a heavy patched OS3.1 system (considering mostly the same functionality). But to be truthfull, I talk about minimum 030 and a graphics card (starting with a PicassoII) here. I don't have much experiences with vanilla Amigas...I only sometimes downgraded by disabling the startup-sequence to run some funny games or very rare apps, that would't start in a full 3.9 enviroment. If you really have to, you can always use startup scripts like mentioned before in this thread by Tempest.
