Okay, from this thread I've got two reasons Camelback may be better than Polar:
(1) Some people bought defective Polar bottles, and some other people bought non-defective Camelback.
(2) Camelback has an optional flip top.
Now, since the Polar bottles I've bought haven't leaked, (1) doesn't apply to me. And riding mostly roads, I don't mind wiping off a bit of dust, so (2) doesn't apply.
After using my Polars daily for 80 days, plus 2-3 uses per week for 3-5 years, I don't know of anything else that would last through that much use. Are Camelback bottles better? just more fashionable? or am I really missing something here?