I'm leaning toward 1 cause of aesthetic preference. Second choice would be 4 though it's too busy for me, yet it fully fits the infested theme best. IMO 3 looks too much like Nekros Raknis, and 2 is better but looks a bit Nyx-like with the crescent shaped crest, would probably match places with 1 without the crest since it seems like it would be an easy callback to the silhouette of the default Ash helmet.
3/4 sketches might have made it more even in spite of the some of profile silhouettes being similar to other Warframe's helmets. Looking forward to more possible designs.