Big differences are....
1. 9nm build instead of 13nm making the chip smaller, slightly cheaper to produce
2. I belive it has a bigger cache
3. can be clocked past 5 gigs
4. 31 point pipeline vs. 20 point (The longer pipe dosen't mean much now until programs start optimizing for it and will be able to operate much faster)
As of now the performance difference is nearly microscopic but when programs start optimzing for it will pull it way ahead of the northwood