That depends on what your after? Long runner intakes are for the most part better used for low rpm operation, where as short runner intakes are better for high rpm operation. Thats really a super over simplication of the matter.
Intake runners are designed to take advantage of resonant tuning by using a series of pulses which occur in the manifold.
To get a rough idea of where the resonant tuning takes place determine the rpm at which the resonant tuning occurs using the approximations below. then compare them to the runner lengths.for example plug in 6000 rpm for each one
2nd Pulse Length: 108,000/rpm (18 inches)
3rd Pulse Length: 97,000/rpm (16 inches)
4th Pulse Length: 74,000/rpm (12 inches)
5th Pulse Length: 54,000/rpm ( 9 inches)
If you match engine components then this provides a slight super-charging effect. However eahc pulse is progressively weaker but provides a broader powerband. If I remeber correctly most manifolds are designed to take advantage of the 3rd pulse because the lower pulses tend create manifolds to long in length to be practical (especially carb manifolds)
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