Symfony [SF] is probably on a par with CodeIgniter [CI] in terms of its use [circa 7-8%] and is a very stable framework. It has lost of a lot of ground to Laravel and in non-tech terms it's really just because the two are pretty similar and Laravel requires less configuration than SF**. Some people prefer `this`, we don't but it makes little difference in the long-run.
SF is really the traditional choice of the corporate and if you love PHP testing and buzz words like ORM [Doctrine] and Entities are your thing then SF will be for you.
SF would not be our first choice, but just like CI, if this is your platform of choice and you'll have good reasons for this then SF is a fine MVC framework to use. Laravel is easier to use, but that's just because it comes pre-bundled with a lot of `stuff` and Laravel is built on SF so it's not that there is really a major difference here, just that Laravel is a bit of a `sugar` over SF and a good one.
Going with SF is a bit like the old aphorism of "No one ever got fired for buying IBM" and SF is used by some very large corporations, but the end results are almost indistinguishable from Laravel in production. If testing, auditing and the word `PHPUnit` means a lot to you then SF is a good choice. **Just be aware that it's more of platform you add to [which can be good] whereas Laravel has sort of done this for you.