Actually, those factors did not matter as much as one thing. It wasn't about having the sickest arrow or bow, or having the raddest draw.

It was actually about the sound of the discharge itself. The Persian scholar Juvayni contended that the sound of the Mongolian barrages epitomized terror itself with their distinctive sound during flight. For those of you have seen Sergei Bodrov's feature film "Mongol" must certainly have noticed that if something was done on the behalf of Mongolian archery, it would have been this.

The Mongolian bow itself was little different from the Turkish bow, which itself was partly of Sassanian design, in particular of the later modular Nawak-type; it was instead the Mongolian draw which added that extra range and punch. However, it should not be called "Mongolian" by pure technicality, because it was used centuries before the Mongolians ever became a unified entity. Let us compare two Sassanian dishes:



Typically early Sassanian era. Nothing too funky.



Late Sassanian style dish, late Sassanian or post-Sassanian, of Pûr-î Vahman hunting. Besides different dress-code and the fact that the latter features stirrups, look at the draw of the bow-strings. Shâpûr II pulls it as far as his ear, in relative terms. Pûr-î Vahman pulls the string all the way to his shoulder.

Now look at their respective grips. Shâpûr uses the finger-draw with his index-finger providing the aim, while Pûr-î Vahman uses a thumb-draw (Which could have been supported by a thumb-ring).

These small things, techniques of application were usually more than enough to utilize more of an advanced piece of equipment such as a composite bow. The Sassanian-style bow with its distinctive siyah (Ears) outlived its late-Parthian roots from whence it developed from the Scythic bow, several centuries well into the Mongolian invasions. The bows did not differ by an awful lot, but the Mongolian arrows, as I earlier pointed out had a distinction to them which instilled fear and potentially chaos amongst the adversary. The exact character of this modification is not known, but must certainly have been effective.