Fire I would say is in fact medium power, but not that muh bottom en grunt, more high speed drive. It's a sail that wil not go completely flat but still totally disappears in the top turn. It has super quick reaction, ie is very, very direct. Fire prefers a certain trim. There is some tuning range for "emergencies" but it works best in its "natural trim"
There is an extra powerful version in sizes above 5.0 called Fire Power edition. This sail has A LOT of power.
Smack is softer and more damped which makes it more forgiving. It has more bottom end and slightly more power overall. It is also an amazing sail in maneuvres, but you feel the presence of the sail a bit more which also means it has a bit more power for driving you through the turns on cross/on. The Smack is super trimmable. You can set it tight/flat, tight/deep, floppy/flat or floppy/deep and it will perform - just with a different feel. A sail you can not go wrong with as long as you don't want a hard feel.
Superfreak. A one of a kind. Super soft and totally quiet (which means more than you might thing). Extremely trimmable and with a HUGE range, best overpower control of ANY wave sail. Will also hold up better to abuse than any other sail. But the feel is unique, so try first. In smaller sizes few people will not love it but in bigger it depends.
Bolt. New for 2010. A four batten very light sail with a unique feel. It has a very good low end power but in maneuvres it is like the sail is not there. I don't know how its done, but it is like the center of rotation of the sail as a whole is in some other spot. It just feels like you're surfing - very weird but cool. Also a sail not everybody will like. Particularly in strong wind. Its not like the sail can not handle it, but when you're powered up, the twitchyness which makes the sail so super throw-about in light winds becomes less of an asset since it's kind of nice to have a sail that stays where you put it in windy stuff.
I use all these sails, so if you have more questions, just ask.