Australia have a luxury with their selections. They have one the great spinners to bowl lots of economical overs and one of the great batting keepers to give the batting depth at 7. This means they only need to play 3 pacers to rotate with Warney, but I hope they play Watson anyway - just to let Lee bowl shorter, sharper spells. England on the other hand need 5 bowlers (including Flintoff), since they can't rely on their spinner to bowl lots and Flintoff is a fragile asset, not to be overbowled - especially early in the series.
That means that while they should have enough bowlers, England's real problem is their long tail, and I think that will play heavily in Fletcher's decisions. He has already gone for Jones over Read and it can only be on batting potential as far as I can see. Now think if England doesn't play Giles and go with Panesar, the tail becomes longer and dodgier, and that will be the main thing stopping Monty.
You only need to compare from 6-9 with Australia. If we play Watson it will be Watson, Gilchrist, Warne & Lee for us versus Flintoff, Jones, Giles(maybe) & Hoggard for England. I'm thinking Aussies win from 6-9 by a fair margin, and that's with Watson, if we play Clarke its an even bigger gap. If Gilchrist finds any form he will wipe Jones for runs and keeping ability and personally I'd rather Watson in my batting than Flintoff (for those into figures, Watson averages 50 at FC level...Flintoff 35). Flintoff will have to bat well - a guy who averages 35 must be in great form to justify a spot in the top 6.
Bottom line is, that if Flintoff and Jones don't fire with the bat, it will be a long summer of collapses and England's top 5 will have to be in supreme form to keep the series close.