I normally ski a HO System 8 68". I bought a HO Triumph 69" for the bigger boys to use, it's the wider more forgiving shape. It does not have a double tunnel like the Burner or the other freeride series - I have a friend with the Burner who could never get comfortable with it. If it were me, I would stay away from any of those double tunnel models - if it were such a great design idea we would have seen it elsewhere.
Whenever the water is rough and/or I just want an easier ride, I grab the Triumph - rides nice and easy and if I have the driver slow down a couple ticks it makes some nice carving turns and throws a good wall of water.
My wife needed her first slalom when I taught her and we bought another wider body ski - the Connelly Outlaw. As with the Triumph, the wider shape helps the skier get out of the water quicker and provides a nice stable ride.
2002 ProStar 197