Why do people always ask the tough questions? And yes this was a real question asked to me.
I can tell you what does not work and why!
Well first of all let me try and put this into context. If you only use a cellphone camera or even a small/compact point and shoot camera then stop now. Those cameras either simply do not need a strap or the one provided for around the neck will work fine. Why? Well they typically do not have any large lenses, the bodies are reasonably light and small. True they are not supreme quality but they do the job (having said that look up my post on computational photography and you may be amazed). Enough said.
Let’s assume you have a DSLR camera, lens, maybe a battery pack on camera as well. Yes a fairly large and heavy camera, no doubt one that does an amazing job, but one that is none the less heavy.
So what does not work?
Well a relatively thin strap is useless, you need to distribute the weight over a larger area thereby relieving the stress and strain.
Leather straps are generally not the ones to look for, oh they are really cool and look great but are NOT functional. Okay so I upset a few, but that I sadly reality. Leather straps could be made wider to help with some of the weight distribution but are no help in removing the heat buildup and sweaty area under them on warm day.
Some, particularly the ladies among us photographers want something that looks ladylike and not like something a SWAT team member would wear. That can be a bit of a challenge, although some companies like BLACKRAPID do have one or two designed by ladies, for ladies.
Oh one other thing, the camera strap MUST connect to the screw in connection on the bottom of the camera or lens – no exceptions here. But the camera has places for a strap you say.. well yes it does.. but sadly they are flimsy and weak connection points that have been known to fail. Use the points that you know will NOT FAIL and drop your gear to the ground.
The best are actually the ones that do look somewhat SWAT team like! Why? Well like the SWAT team gear, they are designed with one thing in mind, how to do the job in the very best way both and in the most comfortable and least tiring way. There is little concern for appearance or looks it is more about function over form. But they do work and once you wear one you will NEVER go back to the old neck strap.
My personal favourite is the BLACKRAPID Double Breathe, a strap designed to be used with a single camera or two cameras!! One of the few comfortable straps made where two large DSLR cameras with large lenses can be carried comfortably and safely to the owner and the equipment.
Not saying there are not others out there that can do the job, but I can say for certain that the BLACKRAPID line is capable of doing the job and doing it well!