Both the 250 and 250AI have been done on the Contender in the past (by at least Jones, Mike B and White), but most folks consider them borderline and too much for it except with reduced loads. If you are not going to drive it at or near its full potential why bother, there are plenty of other good quarter bore choices that don't push the envelope on a Contender (even at their full potential). If you just have to do it, the AI is the better choice of the two for the Contender though.
Other than if the three gents above still do, as far as I know none of the custom barrel makers offer it for the Contender or G2 Contender these days, nor does TC. So that's a pretty definitive answer I'd think. Some of them do offer it for the Encore though.
TC has never advertised/published that the G2 Contender is any stronger than the Contender, another definitive answer IMO.
HTH
L.
(edit to correct and clarify)