Friction comes into play when irregularities or the minute roughness present in the surfaces of two objects, get interlocked upon coming in contact with each other.
In sliding friction, the time given for interlocking is very small and thus the resulting interlocking is not so strong. Therefore with the application of less external force, one can overcome this type interlocking.
While in case of static friction, the interlocking between the two surfaces of the two objects is much stronger as compared to that of sliding friction. So this type of interlocking requires more external force to overcome the friction created because of that interlocking. Hence, sliding friction is less effective than static friction.