Kewell v Emerton is an interesting one.
Never been an Emerton fan, nor a Syd FC fan (waiting for the Sydney expansion club to launch!), but this signing is clearly the safer one.
With Kewell, his technical ability and general class is levels above Emerton and the risk is purely physical. I think there is a big chance he'll cope much better with the lower demands of A-League football than he did in Europe, and the lower intensity training schedules coupled with the lesser match traffic could well lead to Kewell playing 90%+ of the season.
Kewell is also a match winner, whilst Emerton is a functional player - he'll work his socks off and do a job for you, but won't be scoring/creating a lot of goals unlike Kewell.
Here's hoping my hunch about Kewell holds, because he's the most talented player we've ever produced, whether he's delivered on it or not.