I have recently been lucky enough to acquire a second-hand Dell Latitude E4300. This machine urgently needs an OS and will be my test bed for Ubuntu Linux. Dell is using mostly Intel chip sets for wireless and graphics which are widely supported without the need for additional firmware or binary drivers, and has even sold machines with Ubuntu preinstalled, so it came as no surprise that the Latitude played extremely well with both editions. So please bear in mind that the set of hardware is not a challenging one, but probably as good as it gets for compatibility.
In this post I am taking a look at the current two Ubuntu LTS releases that are still supported to help you with the question whether upgrading is worth it.