I used to carry a MaxP Jumbo, mainly to carry food, water, and a book, then, as long as I was carrying it, I'd throw in an extra knife, flashlight, batteries, camera, multi-tool, buff, notepad, pens, etc.
If anyone called it a purse, I'd tell them that it was designed as a gun bag, and then the macho factor would automatically outweigh the wussy factor.
It got annoying that, due to the design, I couldn't switch it to the other shoulder.
If you're going to buy one, I'd definitely recommend finding one that can be worn on either side.
With even a small load of 10#, it would get uncomfortable after a few hours or a few miles of walking. A backpack is always more comfortable for any amount of weight, distance, or time.
A pocket organizer is in a different class completely, as it has to go into a pocket or bag. Pocket organizers are a great way to organize a bunch of small items, but you need a place to carry them, as they're too small for a shoulder strap.