I used to sell rucksacks in a climbing shop in Aberdeen. We basically swore by Berghaus, Karrimor (less so), and Lowe. Much depends on purpose. If it's a trekking pack with lots of pockets, Karrimor always did that well. If you wanted a climbing pack with no side pockets, then Berghaus and Lowe tended to be the start points. That said, both my technical climbing packs are Karrimor.
Just make sure it's well made, has durable waterproofing, has a decent back system and is sufficiently light to not add significantly to the load. Personal fit is a bit of an issue, but less so these days with adjustable backs. Everything else is colour.