My money is on the Imperial Guard for 3 reasons:
1) The numbers are severely lopsided.
2) The Imperial Guard has a high end telepath (Oracle) who doesn't have to be on the frontlines to fight.
3) Both teams have a days prep, meaning that even though Batman can formulate a stellar plan, Gladiator can simply sign an invoice and be given high end Shi'ar munitions and tech that would destroy the solar system combat was to take place in at the word go.
If the League had Manhunter I'd probably lean more towards them. As it stands they have a distinct tactical disadvantage.
Also, which Lantern?
Oh, and Snoop, showing Lobo running through the Imperial Guard minus Gladiator isn't any different than the scans of Deathstroke owning the League singlehandedly when Supes wasn't around.
Though Lobo is badass, no doubt.
In comics, plot devices happen.
Golem's obviously anti-DC, though.