For unarmored infantry composite wins hands down. In 1798 a turkish composite bow was said to shoot 972 yards! (That's the record btw) If you shot a turkish flight arrow at english armor it would probably just bounce off with ver little damage done at all If the english longbowmen could actually manage to get in range and hit the extremely mobile hores archers they probably wouldn't last the battle.

However the main factor to be considered here is terrain and purpose both weapons worked supremely well for their designed purpose and enemy and that I can say with all confidence.

Anyway going back to spears I would think your tactics would vary due envirement and training. Most likely if deployed in mass infantry it would be a darn good idea to have a shelid to defend against peltist. However when using small unit tactics or 1 on 1 you would be more moible, faster, and more effective with both hands on the spear

One of the ways long spears were used in formation was for the first row to thrust under their shield wall with short swords aiming for their enemies' shins while the second row supported them buy using their spears overhand and thrusting down with the hopes of catching their enemies in the spot between their helmets and their chest pieces.

From what I was told, it was a short lived tactic used by Macedonians as they transitioned from using sarissa based phalanxes to a more flexible system based on the roman gladius. It was explained to me by a history professor as being a standard macedonian phalanx, save for the first row of infantry abandoning their sarissa and using short swords underneath their shields. I was told that it was developed as a reaction to being flanked by roman legionarii shortly before the phalanx was abandoned in favor of the legion. Then men in the front and on the sides of the phalanx were more flexible than those in the center holding sarassae, and could turn more quickly to face a threat from a new direction to keep the formation from breaking before any of the spearmen had a chance to turn.

Another reason to stab overhand, if you are in a formation and your spear is held underhand, your spear butt will be low and dragging.  The following ranks can trip on it, accidently kick your point out of line, step on it and strip it out of your hand, plus, the following ranks , if they want to deploy to a flank, has to back up to prevet fouling on the length that is sticking out behind the leading rank.  Overhand is very practicle if you are fighting in a formation, even a loose formation simply to prevent the following rank from fouling the leading ranks, as far as individual combat, in a high stress situation, you will always fall back on what you have practiced.  And if you spend many hours practicing formation combat, you will simply have spent many hours practicing overhand fighting.

never used a spear, and i haven't gotten around to reading classical texts on spear usage...yet.

however, if i was going to use a medium length spear, something around 6ft, i would go overhand assuming i wasn't in a formation. it feels much more natural. however, if i was in a formation i might go and smack the person behind me's head when preparing to stab. plus since one on one/dueling means more maneuvering space i would probably go for larger thrusts that would require the muscles used in overhand (assuming if i didn't get killed within 5 seconds).

if i was in a formation i would go for underhand. i won't have much space for overhand, plus since i'll be neck to neck with other people and working together it would be much more efficient to go underhand and use jabs. plus holding a long pike overhand sounds extremely tiring- more tiring than holding underhand that's for sure.

i've also heard of an anti calvary technique where to turn back a calvary charge, a loose formation of infantry would jam the butt's of the spear onto the ground and have the points in a row where the horse's torso would be. i recall them having a line of infantry standing in front of the spear men with the spear shafts around them. their shields would be locked and swords ready. if the spears didn't turn back the horses, then the swordsmen could take them out. 

/endrambling

For light infantry against heavy armored calvary, underhand where you spport the butt of the spear in the ground is undoublty the best option. Like @ 3:30 in this vid  http://www.youtube.com/watch?v=a3H-Sx1Y6Cg&feature=related


For me preference between overhand and underhand is based on factors like enviroment, if I have one or 2 hands on the spear, tactics, mass infantry or small unit, length of spear, etc.

For small unit "spread out" fighting I'd probably use both depending on whatever opening the opponent gave me.

Anybody know which the Spartans prefered?

here's a quick pic from the bayueax tapestry on the norman invasion. i found it from wikipedia.



the guys here are taking on calvary with overhand spears. not sure how accurate this would be, as the tapestry was made after the campaign.