Firstly, I usually sling the blade open without even touching the blade..I keep the tension tight enough for secure carry, but loose enough for a good flick of the wrist to fling it open.
I prefer holes - prolly b/c my first serious folder was and still is my benchmade AFCK. I don't like the blade design/shape of the spydies, but that's not to say they're not good knives - just not my style.
I picked the AFCK b/c I didn't like studs at the time...in general, I still don't - unless they work exceptionally well. One exception is the BM330 designed by Mel Pardue - I like it a lot, and the stud works great...however, on such a small knife, it's easy to manipulate the stud to open the blade b/c of the small radius when opening...on larger blades, sometimes you have to position your hand funny in order to get leverage on the thumb stud..and then you need to regrip the knife in order for your thumb to be able to reach all the way to push the stud/blade all the way open...
With my AFCK, I stick my thumbnail in the hole, and flick - no need for contact the whole way.
I haven't used any other knives with the stud in the handle, but I imagine they may be one answer to the dilema.
-ZZ