I've used 8125 and 8125g and really haven't noticed much difference. 8125g is supposed to be 92% dyneema, and 8% gore fibers, so it's technically heavier per strength than the older 8125, but it's probably irrelevant.
8125 and D97 are the same except for the diameter of the strands.
The latest and greatest is the new 8190 which is sk90 dyneema which is supposed to be the strongest per mass. So lighter thinner strings are possible. I haven't used it but underatand that the strands are very thin, I think it's something like 2 strands of 8190 to 1 strand of D97.
I'd try to find some 8125 for sale, since the 8125g came out i have seen some decent deals on rolls of 8125. I can assure you it's extremely durable, very little creep. I've used as few as 8strands of 8125, and the creep is still relatively minimal .... Very little stretch too.