AF's new J seats and cabins are really outstanding, on top of the already great soft product, on the 777; solid on the 787.
I love KL's quirkiness, but YRMV re: the food (I've had some weird meals on the carrier!). Cabins and seats are comfortable on their newly-refreshed planes.
Typically, I avoid VS unless I can get a flight on one of their A350s...haven't flown their new A330s yet.
I like Delta One quite a bit, especially as compared to UA or AA. That said, at 6'3" tall, I find the seats to be incredibly low to the floor. Still, I am a Platinum for a reason, and even on the older 767s, the "new" Delta One seats and cabins are solid in my mind; the A350 and A330neos are great, too. As for soft product, the IFE and food on DL are great, IMHO, as compared to UA and AA...but I'll take AF's of VS's catering over DL's.
Regardless of how the above makes you feel, keep in mind the airport you might be connecting through!! If you are connecting through CDG or AMS, the experience may change your mind on the journey (although I have never had issues connecting in AMS, it is big...and CDG is kind of a clusterf*$%). You likely won't be connecting through LHR if you're traveling to Europe since VS doesn't have any connectivity to other destinations on the continent, but if you're heading to Africa, for example, the connections are pretty smooth.