I can't give you XP, but definitely this. And, please, stop posting things I agree with.Hmm - I much prefer the 4e presentation and general feel to 1e-3e tweeness, but it could have done without 500-mile Underdark chasms, dragonborn, Spellplague etc.
I think overall I'd be happy with the 1e Realms but presented in the 4e style. Emphasise it as a wild and unsettled land, and tone down NPC power greatly.