I've had both, well actually i've had the Free 3.0 v.2 Free 3.0 v.3 and the Free 3.0 v.4 and the Kinvara 2's.
The Free 3.0 v.3 are awesomely comfy and I felt happy to run them on quite long outings (25+). They were also awesomely robust and I managed 450'ish miles before needing to swap them out.
The Free 3.0 v.4 started to tear at the arch after a single 20 mile run. Don't know if it's my feet or the poor uppers but they just weren't anywhere as comfortable as the v.3's. Also, my feet got quite hot in these as the upper is quite a closed construction.
The Kinvaras are a different fish, these things are super fast, super comfy, but quite fragile......I reckon you'd be lucky to see 200 miles out of a pair. They hold the foot a bit more firmly than the v.3's and don't have the same role during a direction change. the Kinvaras have a firmer sole than the v.3's (the sloppy sole of the v.3's is addressed by the v.4's) giving a responsive turn of speed.
I loved the v.3's and really wanted the v.4's to correct the difficiencies in the v.3's (the dodgy heel, the ill fitting insole and the squishy sole) and it did but it stuck in a new issue in the upper.
The kinvara, in my opinion, is a nicer shoe - I just wish it was 50g heavier with a little more outer sole. I'd like the Triumph 9 to have a 4mm drop to. Moon, stick, me, never.