In a prep fight? Both have a WEEK. Your talking about Ultron and Brainac working together, these two basically get their hands on each others tech.
I previously posted the Avengers as winners, but then looked back at the first post and saw 1 week prep. Then edited to Ultron's team winning.
The Avenger's prep ain't doing much. All they can prep for is Ultron. They don't even know Metallo and Brainac. And do you really think they can outprep super machines? Ultron can download his entire experience into Brainiac's computers and both Metallo and Brianiac dowload all the info in less than an hour. That leaves them with about 6 days & 23hrs to prep.