When UAL purchased the Pan Am Pacific division in the 80s the Pan Am pilots had traded their pay for work rules. While the PA pilots actual W2s were almost 20% less the a comparable UAL pilot their work rules actually made the pilot cost of operation greater than the higher paid UAL pilots.
Many of the "good" work rules still at UAL are a result of those PA pilots bringing their rest, reserve rules and such to UAL when they added their influence to the UAL MEC.
So the answer is YES work rules are a part of the total compensation differences between the two groups and must be included in any comparisons during the arbitration. It is often said that UAL CBA requires about 12% pilots to do the same work as the CAL CBA.
Somethings are priceless!