Definitely a bit of both for me. There's no doubting that Red Bull Car is well ahead of the rest of the cars in almost every aspect and how it sets him up for the race by constantly qualifying on pole is perfect. Although its definitely not all the car as Vettel is an exceptional talent and as you say he constantly beats his very solid and good if not spectacular team mate Mark Webber. But he doesn't seem to be given quite the same new upgrades and parts as Vettel as there's no doubt Vettel is getting first go and first pick with all the latest things the team are producing, he's the favoured one. In terms of raw talent I have Vettel in a league with just Hamilton and Alonso but the real tester would come to see those 2 as you say in the same car as Vettel, only then would we really find out just how good Vettel is compared to the rest of the drivers and how crucial a factor it is currently of him easily having the best and most consistent car.
Yeah last year Webber forced the hand of Red Bull to consider them co-#1s with his performances, fighting hard for the Drivers Championship which he sadly blew at the end. However this year new World Champion Vettel has stamped his authority hard, and as such the team leaders are happy to relegate Webber to the distinct #2 they had in mind for him in the first place, giving all their car advantages to Vettel, making Webber competing evenly with him even more impossible.
I agree it is both driver and car. It would be interesting to see Alonso or Hamilton with Vettel in the same car. It is a shame that there isnt a way to see something like that, although I guess two of them as teammates is possible, but seems unlikely to me.