Mike L,
I mainly use the Reporter bag when I'm shooting a wedding as I like the quick access to my gear whilst on the move.
It's a large bag though so if I'm shooting something where I'm not moving around as much and don't need the quick access, I'll be inclined to take the mini trekker.
Sport is an example (although when I eventually get a 300 2.8 I'll probably need a bigger backpack...).
Another useful feature of the Reporter is it's compartment for a laptop, although I don't have a need for this yet.
Hope this helps.
cheers,
Merv