Thanks for the replies! I have been really happy with my 40B, it's a great pistol, but I'm doing this mainly because the 40B has a very sharp profile, especially the butt of it, and concealing it has proven difficult for me. It really is a big gun, at 8.1" long and 5.4" tall (and heavy). I would totally keep it if I had the money to have a great range gun plus a carry gun. But the wife would never go for it, she'd rather I diversify, put money into an assault rifle or shotgun.
So I'm looking for a (smaller) carry gun for about $400 - $500 and the XD fits the bill. It's comfortably smaller at 7" long and 4.75" tall (and it's edges are softer). I also want a gun with a higher mag capacity than the 40B's 10+1, the XD has 12+1 and if I'm not mistaken, even more if you get the optional mag extender. Plus with the XD's safety mechanisms I feel it's safely more efficient to carry locked and loaded and not have to worry about flipping the safety off when drawing.
Sorry this turned out like I'm an Springfield salesman, but those are the reasons I'm "switching".
I live in Mesa, AZ and Scottsdale Gun Club has an XD .40 4" barrel for $458.99—so tempting. Plus with Springfield's special they're running right now I can get three magazines and another magazine pouch for free if I buy from a shop, not privately.
I'm not super familiar with all the different types of guns and their prices so if anyone has any other suggestions, I'm listening.
My requirements are: economical, not huge/not tiny, easy to carry, .40 cal, decent capacity mags (for a .40).