I think the TPs are the same when it comes to Business Class so you will have no problem there. Avios will be less than BA usually, unless you're Blue with BA and then it will be similar enough.

Qatar would be the best on board service on this route. I would then probably rate Cathay Pacific or Qantas as next best. BA would come next. You could also try Finnair, but I'd rate BA as better than Finnair.

I would fly BA if you need the Avios though as you will generally earn more flying BA if you are Bronze, Silver or Gold due to the Avios bonus points you get.

From what I know, none of the carriers that fly to Australia charge to book a seat apart from BA, but I could be wrong on that.