Hmmm, cannot comment much on the durability of a wave or bravo. I have only seen a few of them in beach rental places. There they seem to hold up well especially considering the abuse by the inexperienced sailors. I have seen a few getaway's that are privately owned... those look kind of pampered to me - they seem not to go out when it blows.
Rotomolded polyethylene was kind of a popular choice among low $ windsurfing equipment in the old days. To summarize their qualities... They were heavy, flexible (as in not stiff) not contoured (as in no sharp rails) and difficult to destroy. They were good recreational boards - but not at all performance oriented. Repairs require a plastic welding process - but it was not often needed.