This is an edge case, and as soon as multiple users are accessing the AWS Console in anyway, IAM is the only good option, but what if you only have one user?
I've always assumed that if only one person is accessing the account, and they need full privileges, then making a second account (IAM user) with full privileges would only be opening up another attack vector, and actually be less secure than just using the one account. But I started with "I've assumed" and I know it's just that.
If there is only one user, is it more secure to use a pseudo-root IAM user, or stick to just the root account? Why?