I could just leave it at that, but I'll have a go at fleshing out my argument a little. Giorgio Ascanelli, Toro Rosso's technical director has said Vettel has started his career better than Senna. That may be statistically true, Vettel is the youngest World Champion ever, but he's not better than Senna.
There are people who are better qualified than me who can make this argument, people who will have seen Ayrton live and watched every one of his greatest drives. Unfortunately I attended my first Grand Prix mere months after Senna was killed, nonetheless I still think he's a different class to Vettel.
Don't get me wrong, I like Vettel, and the day he went fastest in both Friday practice sessions for BMW at Monza in 2006 I emailed my mate Steve and told him he'd be World Champion (I wish I'd kept that email). But there's a difference between really good drivers and Ayrton Senna. In fact, for that matter there's a difference between really great drivers and Ayrton Senna too.
A cursory glance at Senna's first year in F1 with Toleman in 1984 goes some way to settling the argument for me. The Toleman was pretty rubbish but the Brazilian dragged it to second at Monaco (team mate Jonny Cecotto retired on lap one), third at Silverstone (Cecotto failed to qualify) and third again in Portugal (team mate Stefan Johansson was lapped). Five points finishes (in the days when only a top six finish would give you points) and three podiums in a woeful car and amongst a field containing Mansell, Prost, Piquet, Lauda, Patrese, Arnoux and Rosberg.
His first Grand Prix win came the next year in Portugal. In torrential rain and not the fastest car on the grid he stormed to victory. He lapped the field up to third place, and even Michele Alboreto in second place was a minute behind. That year he totalled 38 points to finish fourth in the table, a place ahead of his team mate Elio de Angelis who at the time had around 100 Grands Prix to his name.
He won a further race that season and a couple the season after before the golden years of 1988-89-90-91 which saw him take the title three times and finish second once. 27 wins in a 64 race period and god knows how many pole positions. If Vettel ever dominates like that I'll eat my hat.
Its cruel that we were robbed of seeing Senna go tete-a-tete with Schumacher and Hakkinen. I doubt the former would be in possession of 7 world titles right now if Senna had been about to challenge him. Senna had that innate speed, innate feel for the limit of a racing car and a circuit that almost no one in the history of motor racing has had, never mind the 2010 World Champion. Sebastian Vettel is a mighty fine racing driver and a deserving champion, but better than Ayrton Senna? Not now, not ever.