I'm debating entering a cake competition. Haven't completely decided.

There is a design that's been done a few times, by different people, in various ways. I'm considering taking it and expanding on it, it wouldn't be a complete copy to any of the cakes I've seen like it. It just isn't a completely original idea.

So in your opinion, which is more important, originality or the execution of a design?

Your skills are impeccable, I don't think you have to worry about that. I would think you could take your idea and run with it. Do some practice runs, but I'm sure your creation will be beautiful.

............which is more important, originality or the execution of a design?.............

Most competition judges realize that there is little totally new stuff out there. Putting your own spin on something is totally acceptable.
Definately execution of design is much more important.

Why do you think an artist would "cover" another singer's hit? It's not the song, it's the way they do it, the artistry of the interpretation, the uniqueness and beauty of the whole.
Go get 'em!

Opinion shouldn't matter... the rules should be spelled out in the competition handbook/judges' scoring sheets. You should be able to obtain a copy to find out the points available/deducted for items like originality, execution, cleanliness, concept, following theme, etc.

"Entries will be judged on overall appearance, frosting technique, (application, texture,
smoothness, etc.), difficulty of technique, neatness, precision, effective use of color, creativity
or clever adaptation of an idea and covering of cake board."

This is the only thing in the rules other than a part that addresses using non edibles on the cake that I can find.

Vary your techniques and as said previously, it's all about flawlessness and difficulty. However, if you enter a large competition where they hand out honorable mentions... originality might get you one. The big, square, black cake in my gallery was far from flawless, but got a lot of comments on originality and I got an Honorable mention.

This is a smaller competition, only the second year for it.

The design I'm looking at as inspiration, isn't from a big name public caker. It isn't a cake that everyone could look at and say it is so and so's cake. There are several on here, with many different variations. All of the ones I have seen are single tiers where I am looking at doing multiple tier look.

I'm still playing with ideas, hoping I can find the time to do the cake. I was also looking online earlier at some none cake stuff that kinda ties in to the basic idea of it.