I'm surprised to see such a split on the Citadel DLC. Either way you go about it there's no wrong choice.
To me, the Citadel DLC is like the cast of a TV show throwing an after party at the end of a series. It's fun, intentionally campy as all F, and I love it. Though how it ends I think would be a great way to end Mass Alex... weird how they didn't make any Mass Effect games after this one. =)
@alex@vinny Just to reiterate what others are saying. The next story mission in ME3 starts the end of the game. You need to do side missions before then. Leviathan is especially important. I personally recommend doing Citadel on an old save after finishing, as a send off.
LAR's comments