Dominant car? Great driver? Or a bit of both?
Vettel based his season on a strategy of taking pole position, blitzing the first two laps and from then on going only as fast as he needed to.
The plan generally worked to perfection - Vettel took 11 wins and 15 poles from 19 grands prix - but it left you wondering just how fast he and the Red Bull could have gone.
In Brazil, I asked him if, with the title already in the bag, he had ever been tempted to just go for it, to really push the car and himself to the absolute limits. He replied that he had done just that in Korea and India, the scenes of two of his most dominant wins. "We were able to explore and sometimes take a little bit more risk," Vettel told me.
Despite Vettel's domination in 2011, there were very few of the runaway wins normally seen when one car is superior to the rest. Quite often, the races looked competitive, with Vettel tantalisingly close to - but frustratingly just out of reach of - his leading rivals.
Vettel and team boss Christian Horner often insisted the Red Bull had less of an advantage over McLaren and Ferrari in 2011 than in 2010. Yet Vettel won only five races and recorded 10 poles in 2010 on his way to winning the championship for the first time.
Let's examine the two seasons in a little more detail.
In 2010, Vettel's advantage in qualifying over team-mate Mark Webber was only 0.053 seconds when averaged out over the season. In 2011, it was 0.414. Likewise, Vettel's average advantage over the fastest driver not in a Red Bull was 0.077secs in 2010. In 2011, it was 0.317. That is a massive percentage gain from year to year.
There are reasons why Webber was so far adrift of his team-mate. Unlike Vettel, he struggled with the new Pirelli tyres, which affected both his pace in qualifying and his tyre wear in races.
The Australian is also physically bigger than Vettel so was occasionally at a disadvantage with the car's weight distribution, which again impacted on both his pace and tyre wear.
Turn One, race one; Vettel already has a big lead as the rest squabble. The story of 2011. Photo: Getty
The DRS overtaking aid, which gave drivers within one second of a car in front a boost in straight-line speed, also influenced matters.
But it is the tyres which were key. Asked to produce ones that spiced up racing, Pirelli came up with rubber that wore out rapidly, forcing a greater number of pit stops and resulting in more unpredictable races.
It is also worth looking at Red Bull's race strategy in 2011. The team may have had a car whose aerodynamic superiority made it the fastest by far, but it lacked a little straight-line speed compared to the McLarens and Ferraris. On top of that, I understand Vettel thought some of his rivals were perhaps better at wheel-to-wheel racing.
As a result, Red Bull's strategy was based on Vettel taking pole position, then opening up enough of a gap by lap three to prevent anyone from being close enough to make use of the DRS system, which couldn't be used for the first two laps. After that, he would measure his pace to those behind, producing a super-fast lap or two if he needed to.
Such a strategy did have its risks. If Vettel found himself in the pack during a race, he would have problems overtaking as the car was set up for lap time not straight-line speed. In other words, an error in qualifying or at the start could mess up an entire race.
Red Bull were caught out a couple of times, notably when Ferrari's Fernando Alonso rocketed to the front on the run down to the first corner in Spain and Italy.
In both cases, Vettel managed to get past again. In Spain, he did it by pit-stop strategy, although it took two attempts, while in Monza he achieved it a brave overtaking move around the outside of the flat-out Curva Grande.
Had it been a McLaren that passed Vettel - a car that was faster than the Ferrari over the lap and down the straights - he might have been sat behind for the entire race.
But team boss Horner was adamant the strategy that Red Bull employed was the right one. "As a team, you have to attack the events," he said. "If you are conservative, sometimes you can pay a penalty. If Vettel was in a situation where he needed a big overtake, yes, a gamble was taken. But it was a calculated risk."
So how dominant was the Red Bull, really?
It had a clear performance advantage in at least nine of the races, of which Vettel won eight - Australia, Turkey, Valencia, Belgium, Italy, Singapore, Korea and India. The other one was Brazil, where he hit trouble.
That leaves five races at which it was not possible to ascertain whether Vettel's was the fastest race car, although it almost certainly was in most of them. They were Malaysia and Monaco, which he won, and China, Canada and Abu Dhabi, which he did not. And the remaining five races where it definitely was not, out of which he won only in Spain.
The first obvious conclusion is that the Red Bull's pace advantage was restricted by the tyres. On many occasions, Vettel could have gone faster but chose not to because he was concerned about over-using the tyres.
At the same time, Red Bull insiders insist Vettel was not always in the fastest car. There were weekends, they say, when they did not think the car was quick enough yet Vettel still managed to put it on pole. Equally, there were times when Vettel was having to drive on the edge to break the DRS and to hold his advantage at the head of the field.
The Pirellis required something new of the driver - an exquisite feel for the limits of the tyres, the intelligence to drive measured races at exactly the pace the tyres and car could cope with and the consistency to do it at every race.
How many drivers could do that?
Jenson Button had a great season for McLaren, finishing second behind Vettel in the standings. The 2009 world champion treats his tyres delicately and, at his best, is as good as anyone. However, his form tends to fluctuate depending on outside circumstances, while he is not the best qualifier.
As for Hamilton, his speed and feel are at least equal to Vettel's but the 2008 world champion struggled in 2011, making too many errors and perhaps not fully grasping the demands of the new F1.
Then there is Alonso. The double world champion boasts speed, consistency, adaptability and mental strength. However, the Ferrari was nowhere near fast enough this year and it's rare that the Spaniard transcends the car's abilities in qualifying, although he nearly always does in races.
That is why, in 2011, Vettel was generally in a league of his own, even on the occasions when his car was not.