I'll preface this by saying that I haven't run a spin pole on a cat, so experience is limited in that regard. However I do have a good deal of experience with composite & aluminum windsurfing masts and booms. I would tend to lean towards aluminum. The advantages of aluminum over composite for this application:
Significantly cheaper, better at handling rivets/point loads, not UV sensitive, overall more durable from a handling standpoint, sufficiently lightweight.
Composite tubes need to be babied. Scratches, impacts, and UV damage can seriously reduce the integrity of the tube. The higher the carbon content, the lighter the tube is going to be, but it is potentially more fragile (many good high carbon-content windsurfing masts have a sacrifical glass inner and outer layer to protect the carbon). Carbon/glass hybrid tubes with 30% or lower carbon content are likely to be equal to or heavier than an aluminum equivalent.