How you aim depends on what kind of shooting you're doing, how close/big the target it and other factors.
The problem comes when you try to make one technique work for every occasion.
Since some level of speed is usually a component in "practical" shooting, you have to take that into account. If you take the time to precisely line up the sights and do a careful trigger squeeze on human-sized target a few feet away then your times will be miserable even though you will probably be very accurate.
On a very close target you don't need to mess with the sights. You can pretty much put the gun out in front of you, move it until it blocks out the part of the target you want to hit and then slap the trigger.
On a target that's a long way out or on one that's really small, you will have to line up the sights precisely and squeeze the shot off carefully.
In between you can work on determining how carefully the sights need to be aligned to get a good balance between speed and accuracy.
Developing an understanding of what YOU can get away with in terms of balancing speed and accuracy requires a lot of time at the range. It's not something you can learn by discussing it or reading it. Once you understand the basics then you have to go practice to get them working for you.
As far as the merits of the various hold techniques (center hold, 6 O'Clock hold, etc.), there are reasons to use one over the other.
6 O'Clock hold is best for precision work with a bullseye at a known range. You can get very good results because it's a very repeatable hold and you can adjust your sights to put the point of impact where you want it to be.
For hunting, trying to gauge how far the bullet will hit above the front sight in a gun set up for 6 O'Clock hold can be problematic so many people prefer a center hold where the bullet essentially impacts on the target so it appears to be centered on and just resting on the front sight.
The "cover up the target" hold is very fast and some folks find it more natural. You lose precision because you can't align the sights very well on something if it's mostly hidden by the sights, but it's not typically used when precision is critical.
At close ranges they'll all work well and the difference in the point of impact will be negligible.
Seriously if I didn't have tight family responsibilities here I would either be there or New Mexico, my other home. In the meantime I go out in my backfield and shoot.