Joey’s got an interesting article on ‘Weight and Durability’ on his blog site.
(disclaimer - my latest purchase greatly resembles the kayaks he is showing)
My main reason for lightweight (quality) kayaks is because I’m protecting a back (that went out on me several years ago).
Carrying a 30# Vs 55# boat a 1/4 mile for my daily paddle makes a great difference.
(not to mention an easy on/off the cartop for the weekend paddle)
I’ve always just taken for granted that once in the water, the weight of the kayak doesn’t matter much, other than quick acceleration (for racers).
However, after reading Joey’s article, it does make sense that weight of the kayak makes a difference in dynamic water - in being able to maneuver it rather quickly.
I don’t have a ‘heavy’ kayak anymore, so I can’t directly compare them, but, sometime I would like to ‘weigh one against the other’ (so to speak) in the surf sometime.