I understand the accuracy debate, but I think it would be even more rare to NOT empty the clip In a self defense scenario. Handguns regardless of caliber lack real knock down power. It would be a rare occasion the person would hit the floor faster than you could fire 6 or 7 rounds from either pistol.
That being said, I have shot both and currently shoot/carry the xds. There is a significant difference in size and feel between the two. XDS feels better in my hands, and I am a large guy with big hands, I already have a Glock 27 which is very similar in size to the 36. So if I a going to carry a bulkier pistol, I will tote the 27. Although, i like buying pistols, so I may just get a 36 as well for fun!