Well one easy point is that rubygem doesn't allow easy local installations. Heck it doesn't even allow specifying all your dependencies — you have to use Bundle

Well one easy point is that rubygem doesn't allow easy local installations. Heck it doesn't even allow specifying all your dependencies — you have to use Bundler for that. More anecdotally, I've had bad experiences with upgrades, though admittedly, the fact that Windows support is a second-class citizen in many popular gems might have been part of that.