Bristol, having held European champions Wasps to a draw last time out, will arrive at Kingsholm in reasonable shape - but Hill knows it represents a colossal mission.
He said: "Wasps last week had been our biggest test of the season so far. This week, I think it will be more difficult, away from home.
"Gloucester have done terrifically well over the past few seasons. They are playing well, and it's going well off the pitch as well - with a great stadium.
"They've amassed a heck of a squad - I think we are all a little bit envious of the money that has been going into that squad.
"They've also brought young players through, which is probably the most impressive aspect.
"They look confident and appear to be enjoying their rugby. They can kick; they can run the ball and are one of the best teams in the Premiership at the moment."
Gloucester, unbeaten at home this season, are determined to stay ahead of the Premiership pack as they build towards visiting second-placed Bath next Friday night.
Head coach Dean Ryan said: "We know Bristol are a very good side, but it is up to us to get our game right and play well.
"Tomorrow (Saturday) is about us producing a performance we can be proud of, because this game is vital in its own right.
"If we can do that then we are capable of beating teams. But it is up to us - we must get it right."