Agree with neither; Haydos is batting well, yes, but I personally think it's because he doesn't have the added pressure of being a ODI opener. Slotting him in the ODI side would put pressure on his Test game again and I think if there's one thing the Aussie selectors have shown by putting Jacques in the Test side it's that they would like him in the ODI side soon.
As for MacGill, you're kidding. He's an excellent attacking ODI weapon, no doubt, but he's a slug in the field and can't bat, recent Test 29 notwithstanding. I mean, could anyone imagine him slapping 4's and 6's with 5 overs to go in the WC? I couldn't. He's been hard done by as far as Test selection goes but Cam White and Brad Hogg offer a lot more with the bat and in the field which is important in the ODI game. Also, with the ball, he has a tendency to be expensive and if someone like Sehwag or some of the newer SL hitters start having a dip at him, I don't think his figures would survive, even if he took 3 wickets for example.
To avoid being completely negative, I'll say who I think should be in the ODI side; Darren Lehmann.
(come on, you all knew I was going to say that).