User blog comment:DaNASCAT/Technical Update: January 6, 2016/@comment-24473195-20160107161235/@comment-1251315-20160107182506

Main difference: UserTags can be used by users individually, ProfileTags can only be added per-wiki, unless Wikia Staff plan to make such scripts available for users to use in their global.js. I guess this generally only benefits new wiki's and not those that have been around for a long time. Plus,

I don't consider how a script is coded, or how much code it uses, as a factor in the benefits: I only look at the features' it offers, and ProfileTags offers no real benefit over UserTags in terms of features, in fact it has a negative as I mentioned above.

It doesn't matter to me anyway, as I never edit my global.js as I have set my global.js in a way so it doesn't need to be edited again as it overwrites whatever tags each wiki uses anyway. :)

To be honest, I'd be preferring Wikia to improve existing features. For example, improving the forum module as it currently exists, rather than replacing it entirely with a totally horrible discussion system that invites the posting of irrelevant rubbish.