Both are sweetly British and lovely!
I don't like the word "crisp" is Crispin. My pet rabbit is named Pip, short for Philip. Peregrine/Pip is a nice nod to the Hobbit. However, there was a female Peregrine as a contestant on a reality show a few years ago. I don't know how popular the show really was, so maybe no one else would even make that connection, but since then the name sounds feminine to me. I think it's actually the -rine ending. It's reminiscent of Catherine.
I'll be the odd man out and say I prefer Crispin, I think the name is handsome and easy for kids to say and understand. I've always had troubles with Peregrine, there's just something about it that makes me feel like it's trying to hard, though in my mind I feel like it's a name I should like... I also think Phillip is rather charming