I'd definitely choose the Cloak. First of all, the Elder Wand would be wasted on me. I do not desire such power (and I'd likely have no real use for such a powerful wand, a regular one would suffice) and I'd be hunted down by others who want the wand. Secondly, the Resurrection Stone doesn't even properly resurrect the dead. In the words to the Tale of the Three Brothers, "The middle brother returned to his home where he lived alone. Turning the stone thrice in his hand the figure of the girl he had once hoped to marry before her untimely death appeared at once before him, much to his delight. Yet she was sad and cold, separated from him as by a veil. Though she had returned to the mortal world, she did not truly belong there and suffered. Finally, the middle brother, driven mad with hopeless longing, committed suicide by hanging so as truly to join her." Doesn't sound very nice. The Cloak would be useful for all sorts of things, such as sneaking around without being seen and, well, mischief.