PBO is regularly used for forestays on racing yachts. It has absolutely no creep but needs to be protected from UV.

Spectra has creep issues but is strong. The word is that it doesn't like shock loads.

Dyneema has less creep issues and is strong. The word is that it can handle shock loads better than Spectra.

Spectra and Dyneema are almost identical chemically but from my research the production process is slightly different which causes the different properties.

I've been using 3mm and 4mm Dyneema lines for trapezes and they are working fine. A couple of months of use with a little chafing over the stays but I'm keeping an eye on it. It is the stuff the kite surfers use, white with either blue or red flecks.

A couple of 12' skiffs in my area use 4mm or 5mm pre-stretch dinghy braid for trapezes without any issues.

I like rope instead of wire because it is light, easier to store/roll, and easy/cheap to replace (don't have to worry about swaging costs).