Why the Cowboys would want him:
Miles Austin is fast, but Ted Ginn is faster and he could add some pizzazz to their punt returns. With their propensity to place Witten and Bennett wide on the outside like Wide Receivers, they could put Roy Wiliams and Ted Ginn in the slots and motion them to either side to create overloads. Missmatch city! I think Ginn has a better than good chance to beat out Patrick Crayton for the #2 WR position and in that 2 TE, 2 WR set, he is actually a #4 option. People say that regardless of where he was drafted, TG Jr will never be a #1 receiver and in Dallas, he won't have to be. He wouldn't even have to be a number 2 receiver. Even though he's under the bright lights of TV cameras, he won't have a lot of pressure on him to deliver and he could help stretch the field and leave the underneath open for their talented TEs and bruising running game.
Why Miami would want Miles Austin:
Austin is a big wide-receiver with plus speed. He would be a good blocker in a run-first offense. He could stretch the field for Henne's big arm and is big enough to beat the CB jams that seem to bottle up our smaller receivers. He adds size to Miami's WR corps. He can be used on quick catch-and-runs and can be extra dangerous on slants if he breaks a tackle. Miami changes out from a small fast receiver who will never be a #1 receiver to a taller slower receiver who has Brandon-London-like size, strength, and athleticism. He gets a lot more opportunities to develop his skills in Miami. Parcells is familiar with him since he drafted him out of Monmouth.
Ted Ginn Jr. on the Dolphins is a over-rated non-#1 receiver struggling to fill the role of a #1 threat in a WR corps lacking a play-making threat.
Miles Austin on the Cowboys is an under-utilized #3 receiver with size and speed and some play-making ability.