Comment 59 for bug 1607535

cbcymru, the problem with installing packages from outside the Ubuntu repositories is that you might not receive bugfix or security updates for those packages. Why? Because you installed 3.6 and the next Ubuntu bugfix update for this package (if there is one) will be numbered something like 3.4+nmu1ubuntu2.1. Since that's a lower number than 3.6, apt will not update your package to that version.

Also, in this case, the Debian package is substantially different so it's not as integrated into Ubuntu's environment. I'm not familiar enough with this package to tell you what those differences are.