Depends on what your farming.

If your farming for...

...meseta with no factoring in drops you can sell your best bet is Agata Relic A rank runs.
...PA Fragments your best bet is Mad Creatures in Parum S rank runs.
...Mission Points is debatable i've heard people choose between Mizaki (sp?) Defense and Omna S rank.
...Bt Str for PM your best bet is C rank Linear Line runs.

I could be horrible wrong on most of this though i could be horrible wrong. Please make your topic more specific next time ^_^;;;.