1DMKIV or 5DMK3 for my type of photography?

I need a body soon!

I can either spend 3400 on either... a used MKIV or new 5DMK3.

I love to shoot portraits at events so autofocus is important... this isn't a studio :l Most of the time I shoot in portrait orientation (90%) so maybe I would need a grip if I get the 5D. Currently the only lens I own is the 70-200 zoom... which one should I get? Which one would you get if you were in this situation?

Would appreciate any help! Maybe a 1DSIII?