Ok, I did some searching and KNOW there were some topics on this but cannot find them now so sorry if this is a duplication.
I am in need of a new hydration system. Currently I have The Fuel Belt Endurance 4 but after 5 years the velcrow is dying on me and the bottle bungees are all stretched out. In the sumer months I use 4 10 oz bottles instead of the 7 oz ones that came with it. I really like it but found that they have the new Helium 4 version(and it holds 8.5 oz so not too much less than the 10) and also found the Nathan Speed 4. I like the fact that it has 2 pouches and can hold more than the Helium 4 in terms of gels. My only concern is that a couple of reviews indicated that the bottles may tend to pop out when they empty. This would be a pain as a friend had the Amphipod one and they would typically unclip and fall out the same way and fly across the trail on our long runs (funny but not when you can trip on them, have a bike run over them etc)