Best for me may be worst for you.
Some guidelines:
Rough side out leather is uncomfortable against skin. I dislike wearing an under shirt just because of the holster.
Get a sweat shield. This makes holstering easier and protects your shirt and skin from the rough edges of the gun. It also helps prevent the shirt from going into the holster with the gun as you holster.
Forward cant makes the gun more concealable because it does not stick out. It helps negate rock back.
A holster will move as the angle of your hips change. It is attached to the belt after all. When you sit, the back of the belt will drop, causing the gun to rock back. Sit up straight to minimize this. Forward cant assists in negating the grip from rocking back and printing.
The holster should not collapse if you plan upon long range days or training. The DeSantis Cozy Partner is a great carry holster, but it's lack of metal reinforcement means it will collapse. During a long range day or training class, this is very annoying.
Kydex holsters are just fine if you keep them clean on the inside. I check mine daily and verify it's clean. They are not hard on the finish if built properly. Either way, some wear will happen regardless of holster material. If you're worried about the finish, don't carry the gun. Training with the gun will result in scratches and dings...clearing a stove pipe guarantees brass marks.
Proper stitching is essential. It should be slightly below the surface of the leather.
Buy a gun belt from a holster company. They know what they are doing. Your back will thank you.
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Resign yourself to a box of holsters that you never use.
I generally dislike Galco. The leather is too thick on many models. They fit too tightly and squeak loudly.
I'd tell you to get a custom holster such as Milt Sparks, but a six month wait is crazy. Other top-notch companies have the same problem.
Keep in mind that overall width does affect concealability. If the loops are together and on the front of the holster, then the holster will be at least 1/4" thicker...which increases the probability of printing and dragging. Split loops result in a flatter package.