Agree. The 480 is going to be better supported out of the box, the 380 will need patches for AMDGPU / Pro. As time goes on given the newness of AMDGPU and the new driver stack and given AMD's history of driver support.. the 480 is the logical choice here.
Did you select Compiz yet in the desktop settings ? Dem wobbly windowz..
I have had the same issues for years with xfwm4, compton, marco etc.. that's the problem with light weight composting window managers getting vsync working properly and tweakable ( like if you need to disable or enable for fullscreen windows ) is tricky and often doesn't work in conjunction with closed source drivers, even with some of the open source ones too. Where are mutter,muffin,kwin work really well and have those options.
I know compton is favored for lightweight but actual performance isn't as good as kwin ( ironic ) , plus you only get a few effects like transparency and lose out on workspace animations, for close, min / max, stacking alt-tab etc... not to mention fades / blurs. Starting a compton config from scratch .. well good luck , most are copypasta.
edit* i found one of the best combos is xfce+kwin. lightweight DE with a powerful compositor. you can easily run both on debian/mint/ubuntu with xfce or mate.
http://www.thelinuxrain.com/articles/tutorial-how-to-use-kwin-window-manager-with-xfce