A longer limb tends to be smoother, all else being equal, but limb design is a factor that often comes into play, with some designs being much smoother than others. Limb core material can make some difference too, but it is very secondary to limb design. A 54" Shrew Classic Hunter with any core material will be much smoother in the draw than a 64" bow that is poorly designed, even if the 64" bow is fabricated from the most advanced materials made. The best person to answer your question about any particular make of bow is the bowyer himself.
Allan