I don't wish to move this thread into a debate over whether Ajmal chucks it or not, he's allowed to bowl in international cricket, and he can still use his doosra, so I'm going to judge this face-off on all things being level in that respect.
I like Ajmal, he's not a defensive off-spinner, and with his ability to turn the ball away from the bat it no doubt increases his threat immeasurably. Like Swann he doesn't necessarily need the pitch to assist him in a big way to have an impact, he's patient, has good variations off the deck and through the air, and has to be considered one of the best around, but at 34 he's unlikely to have enough time to get to the very top.
Currently, for me Swann is still ahead of Ajmal, a Test series in India for Swann still remains a big test for the new and improved Swann, but even the great Shane Warne didn't conquer the opposition there, and it is not the be all and end all, but a good series for him in India will confirm his ranking as the very best.
When Swann isn't taking wickets he's still keeping things economical and working to an alternative plan. His line is generally attacking outisde the off stump, and he too can beat the bat on the outside without having the use of the doosra. Am hoping to see Swann return to his absolute threatening best when we come across Pakistan at the start of next year.