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So I have been shooting a couple of matches and I used to think sight picture was the most important thing but now I'm thinking trigger control is more important. I'm using a U/D and can see the dot start in the middle of the black and ends up making a U. This is once in a while, but once in a while is to many. If it's my trigger finger I would think I would be getting lefts and rights not a U.
Mark II

MKII,

The definition of most important is going to vary with the individual shooter. and to further confuse the issue, that same individual shooter is going to move from item to item of importance as his/her skill or equipment changes.

When I first started, it was stance.
then it went to sight alignment,
then it went to trigger control,
then to grip,
then to focus (target or dot),
then to sight picture,
then to grip,
then to stance,
then to trigger movement speed,
then to grip,
then to trigger placement on the trigger,
you get the drift.

This never ending search for perfection (sounds of laughter in background) will give you decades of frustration and enjoyment.

A smooth nonstop movement of the trigger to the rear is what I am supposed to be looking to achieve. About 1 second duration for sustained fire and 1-2 seconds for slow fire.

Your dot should not be moving around the black because of your trigger technique(TT). Your area of hold should determine your group size, not your trigger. If your trigger is moving your dot around, I'd recommend doing some dry firing against a blank wall and watching the dot to see its reaction to your TT.

Play around with your finger placement on the trigger to adjust any dot movement on the moment of firing. When I am on the line, stance established, before the command to load has been given,I will establish my grip. Then while the slide is still to the rear, I will move the trigger to the rear and watch the dot movement while my arm and pistol are lowered to the table. I adjust my finger placement as needed. If I'm shooting my Rugers or 45's I will also dry fire during the first minute or two of slow fire before loading and fireing for score. I sometimes use up the entire 10 minutes but I figure I paid for the entire time limit so I'll use it if I have to.

I will second all of what stork said and add this...

All the sight alignment and steady hold in the world is of no importance if your trigger finger movement disturbs it in the final crucial moments prior to detonation.

That is called jerking the trigger.

R,
Bullseye

You might be relaxing your grip as you press the trigger.

It could also be fatigue or lack of upper body strength to hold the gun steady. Remember your going to wander some, the trick is to time the squeeze when on target. And with a dot scope concentrated on the target not the dot and the dot will steady it's self out over the target.