Yeah a few other points is access to the equipment my Lowepro Nature Trekker is fine even when fully loaded the expedition harness with waist belt can even out the load, but I am getting too old to go humping it around for several hours... I tend to use the bags that come with the Canon lens and use the lightweight bag that was included.... Access to lens can be improved on the main bag with the addition of external lens pouches

 I have now got a trolley with a waterproof carrier on wheels  ... The best ones are those designed for anglers... If you do use one of these the top loading bags make sense then.. 

As a   final point to consider Airways are now charging a lot extra for baggage being over the limit, and charge an hefty penalty without advertising this!  So check before you leave... And one trip I went on would not allow the fully loaded bag  to go anywhere other than the hold.. Not a good idea to have all your gear down there!! Or let those guys throw it around!!

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt