If nothing else the Doctor has much better PR...
Well he's got a few years on Jack, it's like trying to have Slugo-Cola compete with Coke.
Has he? Ok so Jack spent about a 1000 years buried alive which might not really count as living, but still technically JAck's older isn't he?
I'd have no problems with a Jack-in-space show, as that's what the end of Children of Earth gives us. Jack's gotten the fuck off Earth, he's running from himself, and what does he do? Does he hunt down every last Four-Five-Six and frag those alien smackheads? Does he hook up with the Shadow Proclamation? I don't know. But coming back to Earth and hanging around Cardiff now seems so limiting.
I have no problem with Jack turning up in space in Who, but after CoE seeing him hanging round with space Rhinos and the Shadow Proclamation might seem a bit silly. After CoE Torchwood's really left the Whoverse behind somewhat, and I think it would be a shame to take backward steps.