I chose the 46 over the roomier 60 Liters, and am very happy with my decision. Here are a few reasons why...
5. It doesn't hurt my back after sprinting down a train platform or carrying it for more than 10 minutes.
4. It's not taller than my head, which enables me to sneak it onto an Air Asia flight and past the 7 kilogram / 1 bag scrutiny of security, saving $20 and lots of time.
3. The people on the public bus don't stare in wonder at the monstrosity on my back, and don't have to get up to let me by at my stop.
2. I don't NEED a luggage cart, but I appreciate them.
And finally, one reason I would highly suggest choosing a pack that allows you to move freely and not slip a disk...
1. You can use a squat toilet on your way to the Kuala Lumpur airport with it on your back while holding your other carry on and not falling down into the 2 inches of water around your feet!
See if your friendly neighborhood backpack salesman will let you try this out prior to purchase. Did you stay on your feet? Go for it! Happy squatting!