I do not like the gullwing scar because it destroys a natural landmark- the white roll. The white roll is the raised line of skin between the upper lip skin and the red part of the lip.
As far as the asymmetry, is it more evident with motion? Is it in the width of the lip or the height of the lip?
The Bull horn incision is my preferred approach for reasons you will see in the video below.
I doubt that your asymmetry is in the length of the two sides of the lip; therefore, a seagull incision will not correct the asymmetry
Your plastic Surgeon can determine where and what causes the asymmetry and plan for treating the cause.
ATTACHED VIDEO BELOW:
This by itself may not necessarily correct the problem.
A gull wing lift may be suited to adjust the height of the vermillion border but it may not address the size or fullness of the lips. Occasionally an anguloplasty (corner lift) may also be of help.
The disadvantage of this procedure is a visible scar along the vermillion border and interference with the white roll of the lip.