Brentford winning would be better from a novelty perspective, given that they haven't been in the top flight for 70 odd years, and I would usually always root for the team have been out of the top flight longer to win unless Blackburn or Burnley are involved. I generally find it boring when relegated clubs win instant promotion again, apart from when Blackburn did it between League One and the Championship in 2018 of course.
Since getting promoted to the Championship in 2014, Brentford have been one of the most entertaining footballing teams in the division, have never finished outside the top half, and generally have always been among the highest goal scorers, despite having one of the smallest budgets. Last season they had the 5th lowest wage bill in the division, and the 4 clubs that had lower wage bills than them finished in the bottom 4 league places.