I'm too lazy to install gentoo. If i want an app I want it quickly and pacman will give me that. Unless you have a super fast cpu and can compile stuff nearly the speed that pacman can download and install packages i would avoid it. I've never personally tried slackware but i hear it's super stable. That being said arch has been super stable for me. And if an update ever breaks something for me I just roll back the offending package. Arch makes it simple to figure out how to fix a package update. View pacman.log and see if anything relevant to the breakage was updated. Install old version of package from the pacman cache.