Both Wix and Purolator are made by the same company, Mann & Hummel so the top of the line filters (Purolator Boss & Wix XP) are about identical. IDK about the 20k mile one, haven't touched it yet but it should be on par or better than the Boss.
You can't go wrong with either as they are some of my favorite filters on the market due to how clean the internal construction & how solid the material quality is. The highest end Frams are fine to run but still not as good as Wix or Purolator, and nothing below Frams highest line is worth running imo.