Grant Cunningham is not only a talented revolversmith but a good firearms trainer as well. He has just published an interesting article on the differences between a straight or non-canted holster and a canted holster and which you should choose for your application.
In general, he finds that holsters that allow a straight up and down draw work well in competition events like IDPA but not so well when drawing from a defensive posture.
When I started my drawstroke from where I expected to be in an actual fight — from that threat reaction posture — my straight-drop holster felt as if it locked my gun into place. It was difficult to remove, and I found myself rising to a more upright position just to get the gun out of the holster. That sort of defeated the purpose of the realistic training!
When I realized this (and it took me about a year — I’m a stubborn learner), I changed to a forward-canted holster. That design was not suitable for competition but perfect for realistic defensive shooting practice because it conformed to what my body was most likely to do in a real life-or-death struggle.
The canted holster puts the exit path of the gun closer to the natural movement the hand is likely to make from an actual defensive posture. Put another way, the canted holster places the gun in the position the body is going to find itself in during a fight! It works better with the body’s natural reactions and trained responses than the straight-drop holster does. That makes it easier and more efficient to use under the circumstances in which I expect to defend myself.
This is an excellent article full of good illustrations. Grant’s parting advice is well worth taking to heart – “Pick your gear for the fight you’re likely to have, not the one you want to have.”