Shoulder bags are better because you can shoot out of them. You can't do this with a back pack.
Shoulder Bag > Back Pack
Sometimes.
I have a Crumpler 7 Million Dollar Home shoulder bag and a Kata 3n1 20 backpack/sling bag.
The 7MDH fits a ton of stuff and I mainly use that for big shoot. It fits a 580ES II, 5D MKII with grip and 24-70 f/2.8L mounted, 15mm f/2.8 FE 70-200 f/2.8L IS, 17-40 f/4L, Sekonic L-358 light meter, rocket blower, 2 pocket wizards, Canon charger, and multiple cards, cables, and straps.
As you can image, it's a heavy bastard and carrying it around on one shoulder all day sucks, so it goes only to shoots where I'm not moving around all day and where most of the shooting is done in a certain location.
The 3n1 20 carries just about the same amount, but it has two straps on both shoulders and can support the weight better. When I pack that, I usually pack it lighter too and only take what's needed for trips if I go shoot at a place where I'm going to be on my feet moving from location to location constantly; like at a zoo or aquarium or photo walk.
So they both have advantages and disadvantages. The OP just needs to give us some more information like, how much equipment is going to be used, and what kind of shooting is going to be going down.
Also, I haven't ever seen the Canon back in person, but the price is cheap and it
looks flimsy. The Crumpler and Kata were both over $100 and they have nice thick padding through out. You want to make sure your bag has plenty of padding to survives bumps and bruises because even though you never plan on doing something do endanger your gear, you know when it might happen.