Who cares what it came preinstalled with? My S4 was automatically updated to Android 5.1 and comes with all the stuff that 5.1 normally comes with. I also installed Firefox as my default browser there.

Why bother to upgrade to another phone? The newer phones (except the S5) aren't any better. I love my S4. The only thing I'd bother upgrading to is an S5, since it's waterproof, and still has a removable battery.