I'd go for 16-20mm (maybe) on APS-C. Going ultra wide (esp. at 10mm) can be a pain to correct. The lines should be real perfect and the furnitures not oddly stretched--or maybe that's just my lens (a Sigma 10-20mm) or my pp skills, but still, bottom line is: you gotta watch out for distortion. The wider, the crazier.
I'd love to see your work. I'm nuts about interiors.