Amsteel Blue, Dynex Dux, Dynamica etc etc etc are all made of the same thing and it comes from the same factory. It is called Dyneema SK75! The differences are due to pre stretching. The theory is that once the fibre has been streched it aligns the fibres better and increases the strength and also decreases the stretch.
So buy what ever you think is better because of whatever reason you think BUT they are all basically the same (with a different colouring). Any difference is due to post production stretching etc.
Also the fibre still has 80% strength after 24 months UV exposure. It is used in bullet proof doors in aeroplane coxpits. It was orignally made into rope for the space shuttle space walks.
Dynamica is Dyneema's own brand and is what I use. Amsteel blue is basically the same but the sizes are slightly different.
Cookes sell Dynamica and can arrange the overbraid if you ask.My suggestion is buy the rope you want and get an overbraid put on it. A company in Auckland will over braid anything! 10mm overbraid was about $1.50 per metre.
No those aren't Cookes signs on the side of my truck!!!!!!!!!!!!!

Nissan Terrano coilovers, turboed VH45, Safari axles, and some other stuff.