"I did some research and it looks liek TS1+ or TS+ is made from 100%HMPE ... so dyneema."
Dyneema is a registered trade name for HMPE/UHMWPE--not all HMPE is Dyneema. DSM owns the name "Dyneema". There are cheaper versions, especially from China. I'm not sure if the grading system is specific to DSM or all HMPE.
I've asked, and can't get Brownell to confirm or deny that they use the Dyneema brand HMPE in their materials. Dyneema is considered to be the premium HMPE.
8190 is the highest grade of Dyneema/HMPE available at this time (SK90). I like the BCY-X a little better because the small amount of Vectran incorporated into it makes it even more stable, expecially in higher temps.
For information on what's in any of BCY's bowstring materials, check here:
http://www.bcyfibers.com/Bowstring.php The basic differences are the grade of Dyneema used in the material, whether they are 100% Dyneema or Dyneema/Vectran blends, and if they are a blend how much Vectran is in them.
The higher the grade of Dyneema, the stronger/more durable it is. You will get a little less stretch/creep as the grade goes up.
Vectran is a little heavier than Dyneema, so it may effect speed a tiny bit. It's also not as durable, so you will get more fuzz with materials like 450+ and 452X vs. the 100% Dyneema materials. The blended materials seem to be a little quieter also.
GORE is added to help increase durability--it will have little to no effect on performance.
BCY-X seems to be the perfect blend--very quiet, very stable, very durable.
However, as Ben noted, all the Dyneema based materials are good.
It boils down to personal preferance mostly. It's like a really good archer--when you get to that level, there's no room for huge improvements--you work hard to pick up a little here or there. That's where string materials have come to--they are so good there's not a huge difference in them.
I stick with BCY because they have been the most consistent, have shown me the best customer service, and even though they supply 85-90% of the world's bowstring material they are always looking to try and improve.