Transformered splits are by far the "popular" choice, in so much as they provide ground isolation and there is less chance for something to go wrong. Active splits are good, however, they are expensive and like any other electronic device, they provide another potential point of failure.
All the above being said, I see mostly passive splits, cheap, easy to make, and most of the time they work fine, the only drawback from a technical, recording point of view is that they don't offer isolation, mind you, if something is going wrong, isolation or not you probably have a problem anyway.