Okay, I've made my decision. Still sticking with So Small. I absolutely love IKYW, but its studio version does not hold up to its live performances, so I had to give the edge to SS. If we were voting on live versions, I'd probably vote for IKYW (but if it were the CMA Songwriters Series version of SS, I don't think I'd be able to choose).
Plus, So Small just has such a special meaning to me. It has helped me get through a lot of tough moments, and it was also one of the first Carrie songs I fell in love with when I first discovered her.