[@knighthawk]

Actually, a rapier would have a considerably longer blade than that first one there, it's a weapon designed for maximum reach and thrusting, that there looks more like a sidesword. Terminology nitpick, sorry.

As to which one to choose, I would say that having a longsword that grows would make much more sense - the rapier isn't a battlefield weapon, and it uses a style of fighting that would differ massively from that of a standard european arming sword.