What kind of strain gauge are you using exactly? This is probably a day late and a dollar short, but if you use a rosette strain gauge, it is much easier to determine the various strains. Google rosette strain gauge and you'll find loads of information I'm sure.
Anywho, differences between...
Terribly cheap? You are looking at over $1000.00 for what you need. Compare that to E or S glass and you'll see that it is by no means "terribly cheap".
Bill said "Kevlar is NOT inexpensive" thus he said it was not cheap which is true.
Is there a real reason to use Aramid? Kevlar is not...