How does the feature set of Premier Pro CS6 compare to the CC version of the same?
The first place I'd go is here, as it's Adobe's own comparison chart, comparing ALL features of CC against CS3-6:
Premiere Pro CC vs. CS6 versions | Adobe Premiere Pro CC history
You can also check out the following links for additional comparison info:
What’s the Difference Between Adobe CC (Creative Cloud) vs. CS6?
What’s the Difference: New Adobe CC 2015 vs. CS6, CS5, CS4, CS3?
Creative Cloud (CC) or Adobe CS6 – Which Should You Buy?
You could view these two YouTube videos:
Lastly, you might want to read this "Top 10 Reasons to Upgrade" article:
The Top Ten Reasons to Upgrade to Adobe Premiere Pro CC
In regards to the "Top 10" list, #1 is of little importance to me (code is, essentially, code), #2 is worthless to me (I have my own cloud server), #3 you can create yourself through the use of numerous keyboards, #6 is of no use to me, #7 is of little use to me, and as for #9 I would never use.
Regarding #10, if you really felt you needed it, you could always purchase/install SpeedGrade CS6, as there are still several sources, including eBay, where you can get it. At the same time, unless you're doing actual professional work, using video from multiple camera sources, there's not much of a need. I currently use video from three sources (Phantom 3 Professional, Samsung Galaxy S6 (it shoots outstanding 1080p & 4K video, with excellent audio), & a Canon SX 60HS). This year, I shot my church's Easter production using the Canon, and while not "professional" quality, it did turn out quite nice. The reason I'm mentioning my 'cameras' is the fact that I didn't need anything as powerful as SpeedGrade...I simply did clip-by-clip color corrections as-needed.
If you don't need the power of Premiere, there's always the almost-as-powerful, yet free, which I understand is an excellent product, although it could be considered to have a somewhat-steep learning curve. Other than that, you could always get Adobe Premiere Elements 13 ("old" version) or 14 (just-released) for less than $100. Whatever you get (one of these, or something entirely different), unless you're working on professional-quality final output (which, if you're using a Phantom 3, it's unlikely you're doing truly professional work), any of them will meet...and probably exceed...your needs.