It’s always good @Scubadave63 to be able to ask people who have had a lot of experience over the years of “what we do” so to speak.
And this Forum has a wealth of very knowledgable people, you will nearly always find an answer to that obscure problem you may have.
It is like having an Encyclopaedia of Drone related problems literally at your fingertips.
Full marks “Gents of the GADC” who contribute to solving these problems, some easy, some very taxing,but, you nearly always get there in the end!.
Is there any real difference between DR 15 and 16.1, is it worth updating?
Not a significant difference.
A new “Cut” tab for quick/rough editing the time-line. But really only of benefit to someone building a timeline from multiple clips.
DR is so powerful, and fundamentally aimed at pro video production, with multi-camera / timecode / etc., most of the changes will only be of impact for those users. Most of us will only be using a small part of the basic functionality … and these just don’t really change.
There may be stability improvements … but I’ve never had instability issues. 
Any changes to the basics won’t impact the way you use it should you decide to upgrade.