You're a big guy and you've just had knee surgery. I've no idea what the terrain around Lewisburg PA is like, but if it is remotely hilly, then if I were you I'd be inclined to go for the combo that has the bigger range of gears: almost certainly the triple. And the Defy is a nice bike. But as others have said, don't buy a bike you like less just because it has a triple - you can always stick a nice big sprocket on the back to even things up.