Single Thumbstud.
Aside from appearance/symmetry, double lugs are not necessary.
I carry the knife in my right front pocket. My right hand always grabs my knife, as such my right hand always opens my knife. If necessary (hasn't been yet on my EDC), I can open my single stud with my left hand.
The thumb studs DO interfere when cutting things. Sometimes when cutting a large block cheese or a large diameter smoked meat, my thumbstud mangles the food while cutting into the large item. Times like this make me wish for a Spyderco hole.