I stay away from shoulder mounted stuff. From years of backpacking in
Colorado, I've learned that you can carry weight on your hips much more
easily than on your shoulders. A good backpack rides on your hips and
uses the shoulder straps to keep it oriented.
Think about why kids are going to school with wheeled bags these days
instead of backpacks. The book backpacks have no internal frame, so
they must hang from the shoulders. Over the long haul, this causes back
If you have bad shoulders (like I do from swimming and bicycle crashes)
there's no question that a belt is better.
Also, if you have to do a lot of overhead work, your arms and shoulders
will tire much more quickly with the tools pulling down up top.
I recently replaced my old tool belt, and actually decided against a
nicer leather belt and went with padded nylon. I find it much more
comfortable, as it is very similar to a framed-pack belt. It won't last
as long as leather, but it will be more comfortable, and it costs less
when replacement time comes.