If I'm worried about getting it right the first time, then it has to be the 10 or the 20. I love the things those two will produce.
But on the other hand, I still find myself grabbing my old DL to go out and play. To me it just has that old 35mm size/feel. I wouldn't go straight to love, but there is a soft spot there. The problem these days is I have to grab it when the wife isn't looking as she has taken a liking to using it instead of her old P&S.
One of these days I will probably part with some pennies and go for a K7. I've held one and it's a similar size/feel (to me) as the DL. Right now I can't justify to myself having a 10, 20 and a 7...