I am not an expert in this subject but the cache hit is more and disk read replaced seems to be more in first scenario, turning on low pri, filer will have to spent extra CPU cycles to handle the additional blocks.
Did you try to take a feedback from end user perspective any difference noticed.
If you want some more detailed analysis, then the TR's 3801, 3832 and this working paper WP-7107 give a pretty good view of things. You can gain some added performance configurability by using FlexShare (a.k.a 'priority') to prioritize what gets higher caching priority as well. It will also tell you some of the advantages of de-dupe and flash cache/PAM.