How were they different? What advantages did each ship have over each other?
I've written about longships a few times before:
https://www.reddit.com/r/AskHistorians/comments/28hjbr/how_in_the_world_did_vikings_sail_from/cibmcq8/
https://www.reddit.com/r/AskHistorians/comments/956yc2/what_made_norse_longships_different_from_other/e3rv127/
https://www.reddit.com/r/AskHistorians/comments/ac977f/how_did_the_vikings_not_die_of_exposure_while/