I've had both systems in the water. Neither system is ideal out of the box, but I do prefer the Nomad because the issues I have with it are a lot easier to modify than the issues with the SMS100. One of the main issues I have with the SMS100 is the webbing they use on the harness. It is very soft and doesn't provide much support. It would do fine for backmount, but sidemounted cylinders pull to the side and in the SMS100 that means the soft webbing also pulls to the side. There's no way to replace the webbing without a major modification of the system. The shoulder pads are sewn into the webbing, so replacement would require cutting all that off and attaching stronger webbing with an industrial sewing machine. Unless you happen to have one of those in your workshop, you're now talking added expense. I'm also not fond of the shoulder strap routing on the harness. While it is the same as webbing routing on a backplate rig, it's not ideal for sidemount. It offers less stability with heavier cylinders and, if you keep your backup lights stored on your shoulder straps, they will be trapped between your ribs and the cylinder valves. The rails on the buttplate (actually harness since the buttplate and harness are one piece on the SMS100) are also too close together for me. I'm pretty flexible and can easily do valve drills in backmounted doubles, but I had difficulty attaching the bottom of my cylinders to the rails on the SMS100. All of these issues can be modified, but you'll end up spending more money and a lot of time to make them.
