The SIG factory type like the above pic are fine, as long as you dont get anal about fixing the "gap" between the dot and the bar instead of just shooting with them. Same goes with the "Straight 8", or dot over dot type. For me, they drive me crazy, and my brain wants to fiddle with the gap and I tend to have my attention drawn to that rather than the target and shooting it.
I find the three dots to be quicker and easier to use, as you quickly get both horizontal and vertical alignment with no though or worry. When the gun rocks into presentation, you get a nice, even row of dots, and the bullet goes where the middle one is sitting. Even when you are coming up, or the gun is just below your line of sight, the dots form a small triangle that your brain picks up and they point the way directly to the target.
I've been using the three dots since they first came out and before they were even lit, and have never had any troubles with misaligning the dots. You actually have to work at doing it, and it doesnt look or feel right when you do.