Each has got it's pros and cons mate
Rucksack is good for comfort on long walks but even the waterproof ones aren't that waterproof. I always found myself rummaging about in the bag looking for stuff. Oh and you can't sit on it...... You can get waterproof rucksack covers at camping or cycling shops.
The small boxes (like the daiwa one with the yellow top) are good for short walks. I use mine if I'm travelling light with one rod. You do need to keep your sinkers in the bottom rather than the tray or the whole thing falls over when you open it.
The beta box / breakaway back rest is my favourite. Reasonably comfortable when walking, loads of space, waterproof and makes a decent seat / baiting table. It is tempting to fill it up but as long as you're realistic about what you NEED to take with you it's fine.
It depends really what you need. Personally I'd go for the shakey box / back rest and a cheap (not necessarily fishing) rucksack for the occasional long hike.
Hope this helps...........