DD smiled the other day at just shy of 8 weeks. She does not yet do it consistently. Having no frame of reference, I'd characterise her as a somewhat easy baby. Relatively calm and happy, goes to sleep easily, but doesn't sleep for long stretches.
DS is not easygoing. He's a super sweet kid, but crazy active and opinionated. He also has an angry streak. He smiled closer to 8 weeks, I think? His first laugh was at 11 weeks.