Without metrics based on languages, you’d find it about the same speed or the difference neligable. Further more you’d be testing a boolean/numeric rather than a string. And immediately accounts for a moderator changing their username. Since to get a TwitchID you’d have to parse the tags…
Your bot can call .mods itself and parse the response.
Personally I’d advise just parsing the tags, since you may have subscriber only commands, that need to parse the tags.
Also means the moment a new mod exists you already know they are a mod.
Basically, just parse the tags, it’s better overal