"Ulster were the best team we have played this season and it says a lot about our quality we were able to win. Our defence was fantastic and we took our opportunities when they came," said McCall.
"One of the differences between the sides was that we attacked and got into their 22 we generally came away with some points. But our defence was so good it kept them out.
"Twelve months ago we were very disappointed at how we fared against Clermont in the quarter-finals, especially physically. We have moved on from there and we are a better team now.
"If we have to face Toulon at Twickenham in the semi-finals then it will be an advantage, but not if we end up playing Leicester Tigers."
Saracens flanker Will Fraser, who scored the first try, was named the Heineken Man of the Match, while England outside half Owen Farrell kicked 17 points.
"It's a very happy dressing room and I though we were outstanding all game, especially the forwards - they really worked their nuts off," said Farrell.
"It wasn't always neat and tidy, and it wasn't always clear all the time, but if someone made a break and missed a tackle then there was someone there to cover. It was a very physical game.
"Whoever we face in the semi-final it is going to be a massive test and a step up. We will keep on building and try to get better."