This is the Deceptacons from the Prime cartoon series vs Avengers from the Film. A few weeks after the Chitari invasion, Megatron lands his ship in Manhattan to drill for energon reserves. When S.H.I.E.L.D. demands they leave they refuse and the Avengers are called in to force them to, Megatron decides to handle it with his elite and they drop down to face them after he is called out.
Megatron, Starscream, Knockout, Soundwave, Breakdown, Dreadwing and Arachnid vs the group from the Avengers movie with civilians still in the city. Who kills or forces the other side to retreat wins the fight.
I'm going with bayformers version here since it's pretty hard to compare cartoons to live action movies.
In any case, in an all out face to face brawl/firefight between the 2 groups, I'd have to say I'm leaning slightly towards the Decepticons.
Cap, Hawkeye, and BW will all die within 5-10 mins of the fight. Ironman has got some good weapons but the Decepticons just have more firepower. And as advanced as Stark's tech is, the tech of the Decepticons should be even more advanced.
The only 2 avengers who really stand a chance against them is Hulk and Thor. And although Hulk or Thor can take out a Decepticon on their own, the Decepticons are also strong enough to hurt them, and due to superior numbers I think the Decepticons can knock them both out.
Since he took it from an outside source it doesn't count as one of his weapons. But a Nuke would do some serious damage to them, at least most of them that is, Megatron could possibly survive assuming the blast didn't mess with his internal systems.
The deceptacons are pretty strong, Starscream himself was able to hold up a boulder multiple times his size (he's at least 20 feet if not more) plus the entire section of cave on top of it, as it pushing down on him. And he's physically the weakest of the Deceptacons.
Megatron Soloed a scycraper sized unicron avatar, when Optimus and the others couldn't even phase it together. He survived an energon explosion hundreds of miles in size, still conscious and his armor intact.