Frankly, I dont care whether its a WSOp/AEOp/Nav/3rd pilot or ALM/GE (current J practice), just as long as there is another pair of eyes/another brain in the cockpit who is part of the crew not just an observer. Its always the 'spare' bod who is not totally engrossed 'in the loop' who spots the obvious big mistake/other aircaft/flock of birds etc!