I'm hoping it will be a mixture of both just to keep it from becoming too formulaic.
One thing about JAG back when it was on was that you could tune in one week and it would be a pure legal courtroom-based show, and another week it could be military action and adventure out in the battlefield. So depending on which type of episode you first tuned into, it could determine what kind of show you thought it was. But at least it kept it interesting.
I'm hoping SHIELD will give us a range of different episodes. One week spyjinks, another week fantasy and sci-fi, another week a procedural, another week a political thriller/ drama. It does have the potential to be many things.
I just hope it is more like Chuck or Alias than something like Covert Affairs. I suppose though with the rookie agent there could be some element of Covert Affairs. Could also see it being like Warehouse 13 some weeks.