For him, I'd say prophet series.
My dad has 06/07 K2 Seths, 07/08 Line Sir Francis Bacons, and a ton of Volkl Explosives CHM edition for rocks.
My mom skis on 09/10 Line Pandora's, Has a pair of K2 Nancys and K2 Phat Luv's
If you think your dad can handle a little rocker, go with the Obsethed, if not, Prophet 90