the shield comes with the armor. the armor and weapons are null in this competition. Yes the Spartans were engineered to a certain degree, but i don't know in what way, or what specifically was alterred. But according to the Halo wikia, Spartan III was designed to use "superior tactics, teamwork and sheer numbers". they might be a force to behold as a team, but as a one on one, i think Boba Fett still has the edge. He is used to working alone.
http://halo.wikia.com/wiki/SPARTAN-III_Program