There are some big benefits to going the Creative Cloud route. For one thing, with the Photography plan you get both Lightroom and Photoshop for a really low price with all of the latest features. You also get Creative Cloud libraries which is a super-useful feature especially when used with all of the mobile apps too. Lightroom Mobile is very handy; it's great way to capture actual RAW photos with your iPhone! (Only works on newer models, but it does work!)
Older versions of software may or may not run on newer operating systems. Things in OSs change in ways that Adobe can't predict, so if you want to stay with old software, it's usually recommended to stay with old hardware and old operating systems too.
That being said, there aren't too many issues with CS6 on newer Mac stuff yet.
Also, nothing is stopping you from trying out CS6 on your newer computers and then getting into the Creative Cloud if you're not happy with how CS6 works. You can have CS6 installed alongside newer versions without issue. In fact, a Creative Cloud subscription includes older versions as well (including CS6). So, if you subscribe, you could have CS6, CC, CC 2014, CC 2015, CC 2015.x (the 2016 release), and CC 2017 all installed alongside each other.