The difference between the X-PAC, Uhmwpe and LS21 material:
1. X-PAC material is imported from USA, it's strong and highly impervious to water. And it's lighter than the other two.
2. Uhmwpe material is imported from Taiwan, it's a little tiny stronger than X-Pac, but not impervious to water at all.
3. LS21 material looks cool and it's highly impervious to water, but it's not strong.
So Uhmwpe and X-PAC bags are highly recommended. You choose.