I have the Diamond D with removable flap for my Freedom arms .454 casull and the Diamond D belt holster for my N frame smith. I used the Diamond D extensively in Colorado this year. The .454 is heavy after a few miles. Being able to put the shoulder strap on either shoulder helps with fatigue. You can simply pull it over your head to change shoulders should you need to.
I also have two Simply Rugged holsters, one for my Ruger Redhawk .44 magnum and the other for my Desert Eagle .50AE
Here is what I can tell you. Both will serve you well. The Diamond D seems a little more refined in that the boning process of outlining the firearm is very nice. The Leather is great. The attachment points are black plastic D rings and black cordura webbing with Fastex buckles. This may or may not matter to you. Easy to replace or repair if by chance they should ever be damaged.
The simply rugged has nice leather. The construction is more of a "pouch" type holster. It is secure and I have the flap on it as well. The attachment areas is the difference here. It uses brass plated buckles and hardware and metal rings. They add a minuscule amount of weight. For hunting, I would add bicycle inner tube wraps on these to hide the reflection of the metal hardware.
I had the holster for the Ruger border stamped. The large holster for the .50AE was carved with the celtic pattern to keep it from looking too plain due to its size.
The stamping and carving work was done in a good workmanship manner.
I appreciate the versatility of the simply rugged design. I can use the Chesty Puller harness to use on both holsters (simply rugged) or I can wear the gun on my belt in two different cants or even cross draw on some models IIRC.
The Diamond D is strictly a chest holster.
Hope this helps some. It all comes down to preference. For a dedicated Chest holster maybe consider Diamond D. If you want versatility, Simply Rugged would be your better option.
