Just one more piece of information. Bamboo rods have a "dead space" where the rods join because metal ferrules don't flex. In that case, the fewer pieces to the rod, the better the rod casts in all likelihood. (Note: I do not own a bamboo rod and I'm not a bamboo enthusiast -- but I am applying common sense to the problem.)

This is not true for graphite rods, and modern 4-piece graphite rods cast as well as 2-piece rods in the opinion of expert fly casters that I know (I'm far from an expert).

3-piece rods are being replaced by 4-piece rods because of the travel convenience of 4-piece rods.