The problem with this debate is that one is not necessarily more important than the other.

If you want to go straight into the 'real' workforce after graduation then work experience is going to be more important. If you want to join a graduate scheme or do a lucrative MA then your grade is going to be more important.

They're both valid ways of getting into the workforce and working your way up the ladder.

Long term a 2 week internship is not going to be worth much after your first job, but a 4.0 GPA will always impress and it's something you can use in the future if you need more education.

You shouldn't prolong education to get work experience and you shouldn't compromise your grade to earn a bit of extra money now. But the reality is that very few full-time degrees preclude you from getting work experience.

You can easily do some part-time/freelancing work to get experience while studying or do an internship during the summer. There isn't really a competition between grades and work experience, and which will serve you better depends on your desired career. Assuming you're already certain what that will be.