Honestly, I think the comparison is somewhere between Earl Thomas and Bob Sanders, more the former than the latter.
Earl Thomas was only 5'10" and 202 lbs with 31 inch arms. Not a big dude by any means. But he could fly, ran a 4.37 at his pro day. And he could make plays in the passing game, 8 interceptions in his last year at Texas.
Bob Sanders was actually 5'8" and 204 lbs with under 29 inch arms. He could also fly, it was part of his appeal. He broke out a 4.36. But he wasn't a ball hawk. He had 1 interception his last year at Iowa and 2 interceptions the year before that.
Antoine Winfield is 5'9" and 203 lbs with over 30 inch arms. So he's somewhere between the size of Bob and Earl. And he's clearly a ball hawk. He picked off the ball 7 times with Minnesota this year. That's a hell of a lot more Earl Thomas than Bob Sanders as far as coverage is concerned.
And I believe Antoine Winfield is fast. I have said this a long time, people are underestimating his speed. Every year, Omar Kelly goes to Pete Bommarito's and gets the skinny on who is running well and poised to surprise at the Combine. He recently hinted via tweet about Antoine Winfield being fast from what he's heard. That doesn't surprise me in the least. But I also continue to hear draft analysts predict he will not have good speed, which also doesn't surprise me, because they've been unable to see it properly from the start.