Bali and Maldives are VERY different. Depends on what you are looking for and/or preference. The beaches are way better in Maldives than in Bali. Imagine white sands and crystal clear water. However, you are stuck on an island with nothing much to do which is ideal for honeymoons or those who just want to relax and get away from it all. Since you're stuck on some island too, it can get pretty expensive with the food, drinks and transfer from Male.

Bali on the hand has much more to do - food, shopping, culture, etc. You can stay at the beach for a couple of days and move inland to Ubud for a totally different experience.

Let me know if you need more specifics and/ore recommendations. Lucky has a blog on this exact topic too.