The League One Blades have beaten four higher-division clubs on their way to their meeting with the Premier League Tigers in the last four at Wembley on Sunday.
United would become the first third-tier club to reach an FA Cup final in over 100 years, and Porter, who has scored four goals in their unlikely run, has claimed that the lack of expectation on his side suits them.
"I think there's less pressure on us," he told reporters. "They're the Premier League team so will be massive favourites.
"We've been the underdogs in most of the rounds now and that's suited us and we'll be big underdogs again."
There are currently 43 places between United and Hull in the Football League pyramid.