Smartparens is actively maintained, which for me is an attractive "feature" when evaluating any tool that is to find a prominent place in my workflow. Also, its extensible design allows it to be used with languages and data formats other than lisp/scheme dialects, so it has a broader reach than paredit.
As for wrangling sexprs in, say, Clojure, I think paredit and smartparens are one equal footing. I still stand by my original statement inasmuch as I think smartparens is a worthy successor to paredit.
Have you tried it? If so, what do you think of it with respect to paredit?
(I still use paredit for lisp languages though, and I can't remember if there was a reason for that or it's just inertia/conservatism).