Which VL Ike to use

+Attack is good for maximizing damage, but speed is good for avoiding doubles from units that have somewhat decent speed.

I'd go with +Speed.

+atk is way better, with a speed boon he reaches only 33 spd and that spd isn't enought to avoid being dobled since speedy heroes alway reach more or less 40 spd and slow heroes won't double him anyway. The best way to run him will be using QR anyway so he doesn't need speed to doble anyway and +atk will secure him more ko