Online Seminary is a great option for students with schedules that don't allow release-time or early morning seminary. This is because it can be worked on when you do have time.
With online seminary students can work on the S&I approved curriculum following the current course of study in Come Follow Me. They can work at their own pace, get direct feedback, messages of encouragement, and mentorship from dedicated instructors. Teachers will follow up with reading progress and encourage students to set regular scripture study goals.
Online seminary has the highest 'no credit' rate for any seminary class worldwide (less than 50%). This is because online seminary requires a lot more initiative and effort from the student than in-class seminaries. Unless the student really wants to take seminary and have learning experiences with the Spirit, online seminary will be far less effective at helping them do so because it becomes a checklist activity to finish quickly instead of a learning opportunity through study and thought. Online seminary will take a great deal of dedication and persistence in order to get credit.
Another thing to consider is that student's in online seminary miss out on the social aspect of studying together with others. This can be a benefit for some. But for most, it is a little harder to learn from peers and have conversations with them that help students gain new perspective to the gospel.