Based on other reviews I opted for the 70 oz. version and was very happy with the size for my day-pack. I can't comment on long-term performance since I use it for back-up water storage but the build appears quality and I do like the mouth-piece. I would go with a larger size if I were using it fore more than a day-pack (backpacking etc.).
Pros: Solid build & 70oz is Great Size for Daypack
Cons: None
This review was written in the old system and had content requirements that are different than reviews written today.