Great thread!
My very first Coach was the signature Heritage Stripe satchel in khaki with a pink stripe. I don't use that bag any more because I don't care much for it at this point, but I'm keeping her since she was the first.
These days I don't discriminate between signature and leather, though I do tend to prefer leather over siggy. It all depends on the bag and the style, and it just so happens that more of the leather bags appeal to me these days. I have 11 bags right now, 6 signature, 5 leather.