The small one on the left is the one that I expect to take with me to Nepal and the one on the right is the one I have been using for the last few years for several trips (Egypt, Guatemala, Vietnam, Mexico, etc.). Several years ago it took me awhile of looking around for a camera bag that had sufficient interior space while not being overly big on the outside. Most camera bags have way too much thick padding that I don't need for my uses that causes the bags to be very bulky. I just want something that has a bit of padding and interior dividers to prevent lenses and bodies from knocking together. Actually, I would like something more like that bag, but smaller, for my m4/3 travel bag but I haven't found one. The one I have will work though. It is the bag I bought in 2002 to use with my Minolta D7i.
I put the following in the bigger bag when I took it on travels:
Sony A700 + 2 batteries + charger
Sony 18-250mm f3.5-6.3 + UV filter + polarizer filter + lens hood
Sony 11-18mm f4.5-5.6 + UV filter + lens hood
Sigma 24mm f2.8 + UV filter + lens hood
Minolta 50mm f1.7 + UV filter
Sony F36AM flash + 4 AA nimh batteries
several CF memory cards
several SD memory cards
lens cleaning kit
I also carried the following separate from the camera bag:
Sony A100 + battery (backup body)
Canon A590IS digicam + 2 AA nimh batteries
AA nimh battery charger
This is what I expect to put in the bag for Nepal:
Olympus E-M5 + 3 batteries + charger
Olympus 14-150mm f4-5.6 + UV filter + polarizer filter + lens hood
Olympus 9-18mm f4-5.6 + UV filter + lens hood
Panasonic 14mm f2.5 + UV filter + lens hood
Panasonic 20mm f1.7 + UV filter
Olympus FL-300R flash + 2 nimh AAA batteries
several SD memory cards
lens cleaning kit
I will also carry the following separate from the camera bag:
Panasonic G3 + battery + charger (backup body)
Canon S95 digicam + battery + charger
You can see the size difference. I would estimate that the new gear is about 1/3 the weight. Of course, I don't carry the camera bag around with me when I am out and about. I just carry a subset of the stuff with me. This is also where the smaller/lighter gear will be nice since that subset of gear I have with me almost all the time.