Recently, I stopped by my neighborhood REI; my favorite kayak outfitting store, to look for a spare paddle. My primary paddle has a 230 cm length and aluminum shaft - durable and cheap, but pretty darn heavy, especially when paddling for long periods of time. The REI Paddle Sport Expert showed me paddles made from different materials - aluminum, fiberglass, and carbon fiber. Weight makes a BIG difference! Both the fiberglass and carbon fiber paddles were light weight and nicely balanced. She also got me "fitted" for a correct length paddle for me. In my case, I need a 240 cm length because of my long torso... and the wide cockpit of my recreational style kayak.
So... I did not purchase... yet... what will soon become my "primary" paddle... I'll retire my current aluminum shaft one and make it my "spare" :-O ... I'm leaning towards a fiberglass shaft, 240 cm length paddle that will allow me to adjust the pole so I can feather the blades if so desired. But there are always trade offs... as the paddles get lighter... the price gets higher! :-O The fiberglass shaft paddles retail in the $100 - $125 range while the carbon fiber ones start at over $200. Decisions... decisions!
I also located a good article on "How to choose a paddle." Check it out here.