I would think that in terms of water resistance the lowepro definitely wins out if its got the AW cover. Crumpler bags tend to be hard to open and get stuff out from (in my opinion)
I used Slik U8000 before its extremely unstable. The legs flex uncontrollably and the plastic head cant stay still when I was using a k-m 7D and a tamron 28-200 on it. Dont use it except for the lightest of cameras.