I think Rafe's more lighthearted personality is a nice contrast with everything else going on in the world. Janoah would actually be my favorite character, but I don't think I'd like her as much if Rafe wasn't there as her partner. They're a good duo.
Ah, Jan, she's a firm favourite.
I don't often talk about my thought processes, but I probably based Rafe's character every heroic ww2 soldier I have ever seen interviewed in documentaries - they are modest, unassuming people, often with a joke and a smile.