U-turn's main purpose is not to switch and do damage. 90% of the time, it is used just to gain momentum (the only pokemon who really care about doing damage with U-turn are Scizor and Genesect). If you want to use it just for the momentum, then no attack EV's are necessary.
On the other hand, I can see U-turn being a good coverage move when you invest in attack. The trade off would be between being able to hit Aegislash and Jellicent with Dark Pulse as well as full special attack, or having an extra coverage move (probably HP fire or electric) at the cost of a little power and ghost coverage.
Also,
168 SpA Life Orb Protean Greninja Hidden Power Electric vs. 252 HP / 220+ SpD Jellicent: 148-174 (36.6 - 43%) -- guaranteed 3HKO
HP Electric doesn't let you beat specially defensive Jellicent (you've got a decent chance at beating the utility counter set, though).
On the other hand, I can see U-turn being a good coverage move when you invest in attack. The trade off would be between being able to hit Aegislash and Jellicent with Dark Pulse as well as full special attack, or having an extra coverage move (probably HP fire or electric) at the cost of a little power and ghost coverage.
Also,
168 SpA Life Orb Protean Greninja Hidden Power Electric vs. 252 HP / 220+ SpD Jellicent: 148-174 (36.6 - 43%) -- guaranteed 3HKO
HP Electric doesn't let you beat specially defensive Jellicent (you've got a decent chance at beating the utility counter set, though).