With HMPE--"High Performance or "Fast Flight"--materials, the benefits are: less stretch, less creep, increased durability, and in some cases a mild performance increase (comparing equally well made strings).
8190 is the best of the HMPE string materials. It's the only one (to date) made from SK90 Dyneema. Dyneema in a brand name of HMPE, or High Modulous Polyethelene--a type of super strong plastic fiber. The Dyneema brand is the best made, and most expensive. SK90 is exclusive to BCY.
To put it in perspective, original "Fast Flight" (created by the founders of BCY) is SK65 Dyneema. Revolutionized the world of bowstrings in it's time, now it's considered outdated. It has the most stretch and creep of the HMPE bowstring materials (not as much as polyester/Dacron though).
Jump ahead several years, you have Dynaflight '97, 8125, and it's copies. These are made from SK75 Dyneema--a very significant jump in quality, as the better grade of Dyneema became available.
For a short time we had Dynaflight 10, which was/is SK78 Dyneema. The difference was so small that BCY didn't bother keeping it in their product list, although it is still available as FORCE 10 x-bow string material.
Jump to 8190, and SK90 Dyneema. Another leap in quality--very expensive material to get. On our side of the sport the difference is not so noticeable, but there is a difference. Considering we have bowyers chasing 1-2 fps by tweaking designs, I guess you could say it's a significant improvement.
Then you have the blended materials, like 450+, 452X, and Trophy. These are SK75 Dyneema and Vectran. They actually feel softer, because the Vectran doesn't absorb dye as well, but they actually have less stretch/elasticity. On some bows the Vectran makes for a bit more noise, on some not. It is a brittle material, so while it actually makes the string have less stretch and creep, the fibers break and the string will fuzz up quicker and generally not be as durable. Again, on our side of the sport, it's not as noticeable.
Any of these can be made into an excellent bowstring. Some won't work as well if you try to go too low in strand count; some bows seem to "like" one material better than another, but they have all been time-tested and proven to work great.
For selfbows, you might prefer B-500 or B-55. Both are polyester (commonly referred to as "Dacron", but technically that is incorrect), both are safe for any bow. B-55 is a bit stronger with less stretch and creep than B-500 or B-50, but not in the same family as the HMPE materials.
Which one is "best"? Depends on who you ask, plus a ton of other variables. My preferance in the past was Dynaflight '97, then 8125. Now it's 8190, but I'd still be fine using Dynaflight '97 or 8125.
Hope this helps,
Chad