I'd say the 2015 is the better machine by a significant margin. Retina display, better and faster ports, far better support for external displays, faster Wi-Fi, faster Bluetooth, better trackpad, lighter, longer battery life, comes with warranty.
- I agree with your overall point, and even made much the same one myself above. But to call the 2011 machine a PoS is perhaps a bit extreme. I've gotten 5 good years out of mine so far (with a logic board replacement, true) and fully expect to keep it as my primary machine until at the very least the beginning of 2018 when my coverage for the video issues expires, and quite possibly longer.