Alot of the new Fender single coils can usually be matched up to a Duncan in type of tone, but I think Duncan pretty much beats 'em out, Fenders aint got that mojo no more.
I don't think Duncan and Fender Pickups match up that well in the same guitar. If you're going to use Duncans, my advice would be to use them in all 3 positions.
As for the SSL-1 > it's my favorite Duncan Single Coil. Very True to original vintage tone. Nice and glassy, bubbly.
In a Strat, I use SSL-1's in the neck and middle, and an SSL-3 in the bridge....