Objectively as in speed at which content is released, range of content offered, accessibility, class balance, etc. Not to mention more superficial things like quality of graphics and models etc.
Subjective things would be whether you like a raid or a storyline or whatever.
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Doing both 10 and 25 on NM doesn't make you "hardcore" lol.
I played in Wrath and I guarantee you, everyone was trying to do both 10 and 25 every week. There wasn't even a question. And I was in a super casual guild back then.