Apples and oranges, foxes and hedgehogs. As others have said, War and Peace is better as a "novel," but The Brothers K is better as philosophy or as drama. I have always enjoyed reading Dostoyevsky more than Tolstoy, but I can understand that this is really just a personal preference. The Rebellion chapter of Brothers shook me when I first read it as a teenager and was almost as powerful when I reread the book fifteen years later.
I reread most of Dostoyevsky over the last few years, reading the Pevear and Volokhonsky translations that were not available when I first read the books. They have done a wonderful job. Crime and Punishment, in particular, is much richer in their version than in the old Garnett translation I first read. Their translation of War and Peace just came out and I am looking forward to checking it out. Who knows, now that I am older, maybe I will prefer Tolstoy.