I wish they'd do both. Peter first, then pass the mantle to Miles somehow (through retirement or death). I think the legacy aspect of Miles trying to live up to what Peter did would be really cool to explore in the movies. I don't think we've ever seen a real "successor" storyline in a superhero movie franchise. Plus how cool would it be to have Peter and Miles potentially working TOGETHER on the big screen? A Spider-Men buddy-hero comedy!