Congrats on your upcoming marriage! Both islands are very beautiful, but I personally prefer Maui. Both have some beautiful beaches and hotels, but it can be somewhat difficult to find much of an exciting nightlife on Kauai. For that matter, it's hard to find a restaurant to serve you between 1:30pm and dinner. For that reason, I much prefer Maui for the perfect blend of untouched beauty, laid back island life, and yet some luxuries of city life within reach. But, if that stuff doesn't matter to you, than either would be great choices. Best of luck!