Depends from which perspective you look at it.
If its at terms from who tops their respective league, Arsenal are, but if you take it from Champion's league clean sheet pov, Arsenal are not.
If you look at it from previous encounters, I think Arsenal had a good record against Italian teams, while Juventus are seasoned contestants that have had good records of advancement.
Considering, Arsenal underdogs, is a little bit harsh especially when they had the upperhand against Juve in the 1980 Cup Winners' Cup, and a victory each in 2002 Champion's League group