I've used twig quite a bit. Its leagues better than Smarty in every way. I heartily recommend you give it a spin. Having autoescaping built-in is a powerful and fantastic feature.
Smarty can actually do auto-escaping. Twig was specced in the Smarty 2 era and Smarty 3 and Twig ended up solving the problem in very similar ways. My biggest gripe with Smarty is how damn unprofessional it is - backwards compatibility breaking changes on point upgrades for example, and the code and "API" (I use the term loosely) is a mess.
