I can definitely say I'm happier when being paid for freelancing. When I see that cheque I know it's a result of the sweat and time I put in a project.

Salary on the other hand is just cash being transferred to my bank account. I never physically see it, no one hands it to me. It's just a number in my bank account that I don't check often.

I bet I'd be happier if my boss handed me a cheque every two weeks instead of doing bank transfer. It's an emotional "I have to see it to feel it" thing.