Yeah, bring blood back and make it rated M. For me, shooting someone and no blood comes out is like power rangers. Halo needs to be realistic again.Actually, no blood would fly out of the entry hole, because the blood doesn't magically start flying opposite to the bullet's direction of travel. A little blood would leak out afterwards, but you wouldn't see this because it's contained within the armor. Assuming the bullet makes an exit, a small amount of blood might come out with the bullet, but since most of the damage is contained in the armor, the amount of blood that would exit the armor would be droplets. In that respect, Halo 5 is the most realistic with respect to the amount of blood.
You're all free to wish for more blood, but don't pretend it's for realism, because huge showers of blood are not realistic.
That would be the case with SPARTANs and projectile weapons.
Though with the marines that have less protection, some wearing regular hats/caps or nothing at all occasionally being the case, it would be a bit different story depending on weapon.
Covenant species, Flood & such could be their own thing but thats different thing alltogether.
Though even with SPARTAN armor, how to handle all of the sci-fi weapons & their effect to said armor (shielded)?
Likely something of forerunner design would leave some major damage upon impact, likely not blood but just burnt hole on point of impact.
Then there is the neck/jointshots, those shots that don't hit the plates or other hardpoints of the armor, that would likely look different depending how would the undersuit react to different types of futuristic bullets.
Likely, if the shot would hit an artery blood would spurt out of the armor after being shot, resulting in puddles & somekind of afterspraying.
And the question is that what type of damage would futuristic weaponry do to a futuristic helmet? Obviously likely not a massive spray, so I would go with your line of small spray of blood that travels with the bullet.
So I would think depending on the type of shot & point of impact the resulting "realistic" (using term loosely in sci-fi) amount of blood would vary even significantly though mortal shots would likely result in puddles from arteries being open.
While alien weaponry could result in more burn type damage with minimal blood.
Explosives would be exception with more noticeable damage, if defence has evolved, so has offence.
So if "realism" would be to take away more early game type bloodsplatters, it would also bring with it explosive damage & other rather gory aspects.