This Is What I Think as I had Them both side by side 
I may be wrong as they both look fairly similar.
Discuss!
They’re both the same.
They’re the same, both the normal MK VI from past Halo’s.
Yeah, now looking at a chief screenshot, it does look quite different 
This two helmets are the same, Master Chief’s helmet looks different a little.
If you’re asking about the new “Cortana special Mark VI exclusive to Master Chief” helmet being in multiplayer the answer is NO.
On topic: they’re the same helmet from all sides, the old MK VI
How to unlock Mark VI Helmet for your Spartan in War Games and Spartan Ops:
Pass the Campaign on Legendary.
> > They’re both the same.
>
> Different Description, Hmmm…
>
> 1
>
> 2
The second one is describing the chest piece
> > > They’re both the same.
> >
> > Different Description, Hmmm…
> >
> > 1
> >
> > 2
>
> The second one is describing the chest piece
oh yh… derp
> > They’re both the same.
>
> Different Description, Hmmm…
>
> 1
>
> 2
When they took the screen cap for the second picture the image for the armor didn’t change. It’s the description for theRaider armor.
