I was fortunate enough to have my kids early, so being a mom always ended up being a better gig than these other parts that came along. So I always justified not really working a lot because I had a family.
I don't know if it's harder but when you're playing a real person you want to honor their memory - even if they're a criminal or someone that the public loathed. That can be challenging.
When I do the music, I make the musicians listen to what's happening in the film. That way they treat the dialogue as if it was a singer.