Theoretically, the longer intake provides better low end response up to a certain length. Shorter runners are said to be better for high rpm applications.
If you want to dive deep, There is a optimum length for any given engine using a formula that you can find online. When you tune to the proper length, the pressure wave inside the runner can help flow if you get it exactly right. It's sort of like exhaust scavenging but on the intake side. These waves bounce back and forth to create very high velocities. You can tune to a 2nd or 3rd or 4th order harmonic and so on with different lengths.
I think it's pretty fascinating how people figure these sorts of things out and engineer engines utilizing these phenomena's that can't really be seen with the eye.
If you want a good compromise, go with a medium length. A 28mm is pretty big so longer may provide you with better throttle response.
