Quit saying "upgraded Venom" you prat.
His strength was increased, but having a 2nd symbiotic lifeform trying to bond with the original and Brock drove Venom mad. Hence the name of the comic series.
Venom is no match physically for Juggernaut. Upgraded or not, he's not in Jugg's league, and i don't know anyone dumb enough to argue that point.
But in the Madness they slugged it out because Venom was protecting someone that Juggernaut was hired to kidnap, and Juggernaut busted through a wall to get him by surprise. In a straight versus match up, Venom would actually use his spider-like abilities to the best of his advantage.
ultimately the winner is still Juggs...but the fight would be more interesting if it took place in an open street instead of an underground apartment complex...or whatever housing that was.