alea iacta est

Perhaps you are refering to the pre-marian legions which often had a good deal of poorer soldiers who had poor or ineffective armor. Some histories talk of soldiers who meerley bought metal plates and tied them around their chests.

It is difficult to say strategicly. Obviously it would have been croosing the alps would have been and extrordinary task even for Alexander and it is questionable if he would hae made it at all. A much easier course would be to cross the adriatic sea and assault south east Italy, but as Alexander had few or no ships this would have been logistically troublesome. Tactically however the contest is not so close. While the maniples were immensly strong the cavalry or equites were very weak. I have little doubt that the companion cavalry would sweep them aside like a cloud of dust and as the phalanx is all but invinceable from the front the Romans would stand little chance. Still bringing horses across the alps would result in a great many of them dying. Couple that with the difficulty of feeding a massive army by land across the alps once the fanatical Romans burned to crops north of the Po river and Macedon's starving troops might soon find their fantastic soldiers and their invinceable leader in a close contest with the sons of mars.

I would have to go with being part of the pricipes. A nice big sheild for protection, some pile to kill the charging enemy, a short sword to shank the ones who survive, and some hastati to rush in and soften up the enemy first.

Without question! Scipio was the greatest captain of the ancient world! ( And maybe the modern world also!) He studied his enemy and worked his own tactics out before hand. So did many other succesful commanders for example Alexander the Great.

But in all fairness I think you should note that he had a distinct advantage we he fought Hannibal at Zama

I have to go with Julius Caesar what with the briliiance with which he executed so many battles against not just Gauls, Britons, Germans and even other Roman legions. Few other generals can come close to the victories he chalked up on his many campagins.