For a general army list, the split would seem the best. It offers versitality. Many people discount the noble flamer, and that is a grave error.
As far as multimeltas, I have seen them used to great effect. Against any army with armor, they are a huge threat. I've watched IG armored companies take massive hurt from an SOB army loaded with MMs. Granted, against a well diversified army, the multimeltas will be less useful than other high powered, high cost weapons.