I know you guys were having the discussion and I know it's subjective but if I can just chime in a little bit of my opinion?
Why I think ASM will be more faithful is purely based on the vibe I'm getting from the characterizations. I can't truly say until the film comes out, but that's what I'm feeling. On the other hand, the origin, among other aspects such as the costume and story are either altered or being more fully explored. But in the end, it doesn't seem like those changes will end up changing the characters' personalities and how they embody the character. Peter will still be an awkward, shy, loner/nerd (whose intellect will be emphasized). Spider-man will also be a jokester, we can also already tell that his movements will be much more fluid and kinetic (spider-like). Compare this to a faithfully done origin, but with characters who were more or less just faithful in name and lacked the personalities that I at least knew from the cartoons and comics. The character still embodied the essence of Spider-man, but I personally couldn't believe that the character I was seeing was really Peter Parker or Spider-man but instead was overly shy, always lacking confidence, continually pining over a girl, lacking a sense of humor and just how little development the character actually went through. So yeah, I'd say both about even in terms of faithfulness both are lack in some areas, but in the end, I'd argue that how true and well ASM portray these characters will ultimately be a deciding factor for me. If I can physically and aesthetically recognize him as Spider-man and Peter Parker, but also emotionally recognize and connect with him as Spider-man/Peer instead of getting annoyed and wishing bad things on him, then that's great.
