One major feature that's new to the 2015 and above versions is that the UI is now off of the CPU, which makes interacting with the UI much faster, which is my own workflow save a tremendous amount of time and cuts down on a lot of the frustration factor.
If you are working on a team, the integration of Libraries might be useful, which lets you share assets, colors and fonts in-app, and also can function as a built-in workaround for Ae's lack of a color palette.
Not having to RAM preview everything is nice as well, and the uninterrupted preview is useful, albeit it can take a bit getting used to.
I've not used this on a regular basis, but you can also create Live Text templates that can be edited inside PrPro without having to open Ae.
There's also Typekit integration, native support of some QT codecs, as well as lots of other goodies.
[Robert Smith]"Since Cosa 1993 we upgraded three mac AE licences at every opportunity.
Since the pay monthly CC our team stopped upgrading and have been using Cs6 quite happily.
We wondered if it is worth upgrading, Q: appart from the cinema4d, what facilities in cc are not available in Cs6"
I think it depends on which features you find useful. I'm a big fan of some of the smaller UI behaviors and enhancements like layer snapping and automatic folder creation for image sequences. I also find the key cleaner, updated Warp Stabilizer and 3D tracker useful... Cineware also keeps getting better with each update IMO, YMMV. ?
It's not an "upgrade" per se. There are some new features and enhancements of course, but changing out a working system is a bad idea because you'll have a million little "Oh yeah I forgot about that" and suddenly you're off looking for some doodad buried inside of some other doodad.
Get a whole new system drive and start there with CC. Run parallel systems for awhile.