I don't really get the argument that says that the team would be better with both Gards and Gordon in the lineup. Fullback is generally regarded as one of the two most important positions on the footy paddock. If you've got a good one, you want them to play there.
Case in point: South Sydney. In 2011, they preferred Nathan Merritt at fullback (when first stringer Rhys Wesser wasn't around), while Greg Inglis played in the centres. There's no denying that Merritt is a fine player with a great try-scoring nous. Inglis is also a match winning centre. Johnny Lang's reasons for playing them in those positions is entirely sound - albeit strong evidence to show that Lang's coaching method was outdated. He hadn't caught up and realised just how important fullback is in the modern game.
Cut to 2012. Maguire comes in. He's much more in touch with the modern game, and immediately recognises that Inglis will be a superstar at fullback. Merritt is shunted back to the wing. It's no coincidence that Souths dominated last year - it was primarily on the back of Inglis' fullback play. Inglis' ability in positioning and particularly ball running were far superior to Merritt, and this translated directly into results.
So the question to the Gardner apologists is this: why would you play a kid who is an average fullback (I'm being generous here) and has proven inability to position himself adequately - both when collecting downfield kicks and defending kicks on his tryline - over a proven fullback who showed incredible ability both ball running, passing and positioning while playing at 50% at the back end of last season?
The argument that you want to fit both of them into your team isn't valid - it's an outdated, Johnny Lang era concept. Feel free to offer any rebuttal that doesn't go down that track, however!