Benefits - removal of hormonal aggression (usually works but not always if its not based on hormones), less buck grease (softer fur), NO chance at accidental pregnancies, no chance at testicular cancer (very rare anyways), so really no true health benefits, surgery isn't very invasive and they heal quickly.
Con's - possibility of neuter abscess later on, complications with surgery
Benefits - NO chance of accidental pregnancies, no uterine masses, pyometra's, decreased chance at hormonally driven tumours (mammary and Pituitary tumours), if tumours do occur they grow slowly (have heard seen this but haven't got the hard facts just experience).
Con's - complications with surgery as it is more invasive, need good vet.
Speutered animals seem to live longer because of the removal of the stress to mate and procreate.
If you are trying to decide whether to neuter males or spay females in a soon to be mixed colony, its preferable to spay the girls.