I also use the Lowepro Mini Trekker AW - purchased off Amazon last year, and have been happy with it ever since. Its been through some pretty awful weather when I've been out hiking, and none of my camera equipment has got wet or been damaged. There's lots of room for a body and a few lenses, and you can completely customise the layout of the interior, because all the compartments are secured (very firmly) by velcro. I really like the tripod holder on the back, though it can be a bit fiddly.
I'm able to keep my entire camera kit in it. Others made need something bigger, but if you're out hiking for a day or two, I think it'll do everything you need.
I've not used the Primus AW, but Lowepro kit is excellent in my experience - I'm sure it'll be great, so long as its big enough for what you want to carry.