Well, to get down to basics, your head is held on with bolts. Threaded on one end and has a hex head on the other. Studs are threaded on both ends; you use a hex wrench to thread one end into the block, and the other end sticks up. You put your head over the studs, then thread on a nut and torque.
Studs are typically higher quality than head bolts, and have a higher tensile strength. I believe the clamping force of studs is higher than a comparable bolt also... basic enough? Haha
If your truck is daily driver, Id go with o-rings. Ive heard they last longer than firerings. Never ran either so I cant really give a first hand account. I think it has something to do with heat cycles...
Ive been reading alot recently about studs popping, and its been every manufacturer. But they are a necessity so you dont lift the head off the block.