Deliria makes sense. I've seen both films and they're completely different but Sabrina's role could've fitted into either. I have a strange obsession with her, Im afraid.
I think you're dead right about Argento's relative lack of range, which is frustrating because in interviews he seems far more interesting than his films often suggest; far more than a lot of filmmakers I prefer, even. I half wish he'd been more adventurous in his choices. I really don't think we'll ever see the best of him so long as he sticks within the limitations of horror movies. Those limitations worked perfectly for someone like Fulci but I think Argento's general style has always been slightly hindered by them.