Marc, Either can be done, but it sounds like the casing is restorable here by using wood putty to fill and reshape. My personal preference is Minwax Wood Filler. It can be applied quite thick without shrinking and cracking like many other fillers do, and it stains out very nicely. Just recently repaired some kitchen cabinets this way that had 1/2" deep gouges missing from the very same reason. Good luck!