Backlash
I ordered that ppv. Everyone expected Benoit to lose the title to either Triple H or HBK. For one, it was in Benoit's home town. Secondly, the poster for Bad Blood, featuring Triple H and HBK in a cell, was released before Backlash. You could looking at other wrestling sites and see that people predicted that Benoit would lose the title before Bad Blood. Not to mention, it was uncommon for Triple H to not hold the title.
Other reasons the Backlash > WM 20 includes the crowd which was much more lively at Backlash than Wrestlemania. Triple H was already a hated heel, and HBK was the biggest heel in the match. Benoit, on the other hand, was the clear cut underdog and favorite compared to Wrestlemania 20.
IMO, the win at Backlash did more for Benoit than Benoit's win at WM 20. Benoit still didn't look or feel like a main eventer after winning the title. By defending the title again. and making HHH and HBK tap back to back at ppvs, Benoit proved himself.