The Extra 300 has the engine mounted sideways.

I forgot that the Super Sportster kit has been rereleased... I always liked the look of it. Compared to the Extra, it has more block carving and sanding -- to form the nose and fairings for the wings and tail pieces (I love the way the wing fairing is done on the Extra... foolproof way to get the effect that I really had to work for on the ol' Fun One). The Super Sportster has less sheeting because the turtle deck is covering directly over stringers. (Its engine is mounted upright and not cowled.)

Like Wogz says, it is worth a trip to www.greatplanes.com to check out the instruction manuals -- you can really sees what you're up against. I agree, too, about the instructions: Sig and Great Planes both do a super job on them.