ok so i was looking at no hearts pics and in these two pics no heart has two very different amounts of hp

I noticed that; one might be No Heart and the other might be the shield.

if your right then thats a lot of hp for the shield. i all ready feel ten hours of my life going away to fighting no heart once thats if he doesnt kill me in the first five seconds

Different stage of the battle, perhaps?

Final Xemnas had more health than Armour Xemnas.

i would have to say what keystrike said its most likely

Yes, in the second one they are not fighting NO HEART but rather his weapon.

i think difference was difficulty,who knows,the harder the difficulty,the more hp he has

In one picture, they are fighting No Heart and in the other picture, they are fighting his weapon.