Apparently, both are the building pillars for a successful startup. It is good to have a great idea for startup but the execution of that idea is what makes a startup successful. You may be having a good infact great idea but if you are not smart enough to execute that idea in a proper way, then the idea serves no purpose.
To execute the ideas, tasks is a challenging job. One needs to be smart as it involves taking proper decisions, optimizing the ways and so on. So if one knows how to execute their plans or ideas well, such startups can be more successful than the startups with only great ideas.