I went for the Kata rucksack because it's subtle, doesn't have a logo or design that screams "I'm a camera bag, steal me" because I carry mine all the time in London.
I do like a shoulder bag for accessibility, but not for lugging around all day, it gets to heavy on one shoulder and if you're at an event shooting with lots of people around you, you just end up knocking people with it.
Besides, at weddings, I tend to put the kit bag down and just have a camera on each shoulder with a different lens on each.
When I'm out for the day with the family, at rucksack is more useful to put additional non-camera stuff in.