JOE HAHN is far better! I know this because Joe actually plays his instruments live, David Guetta on the other doesn't always.
My sisters boyfriend works in the music industry and he has set up the projections for one of David Guetta's gigs, he was shocked to find that when he looked at where David will be standing there weren't any turntables for him to use! He watched the gig and all David done was wear some headphones and put the wire in his pocket...this is not acceptable especially since he is a professional.
I think that no Linkin Park members should be replaced. Ever.