The Smith seems to be the best of the bunch. More satisfied owners than I've ever seen for a firearm. I'm sure the Sig is just fine as well but the Smith looks and functions like a real AR. As far as your original question regarding a flash hider, the answer is no. There are compliant models out there that do not have a flash hider.
As for the MOE, if you like the MOE furniture, then the MOE is a great value. Much cheaper than trying to add the Magpul gear yourself after the fact.