Sympathize with your dilemma, it's always tough to "let one go." Since you still have the Springfield it should make the decision easier. My only question is carrying iwb, how's the safety rubbing your side? Does your holster lack a body shield? I love the 1911 but if I'm carrying that platform I want a body shield on my holster that engages the thumb safety in the "ON" position.
As much as we 1911 fans rag on "combat tupperware" it's mostly good natured ribbing. They're fine weapons to be sure and from my POV still have the advantage of consistent trigger pull from first shot to last.
Is there any particular reason you'd rather trade the Kimber and keep the SA instead of the other way around? Just curious really, which trade would be a better deal on your part? Overall I'd say go ahead and trade for the Glock (if you know the G19 suits your taste).