For me it totally depends on the amp in question. If it's an old Marshall, I'll take the boost. If it's a more modern amp like a recto, I'll take the EQ in the loop.
Overall, in general I tend to think of boosts more as adding gain/chunk/saturation than adding tightness...but i guess it depends on your definition of the word. Maybe my definition of "chunk" is someone else's "tight." When I think "tighten" I think of removing frequencies that are making the sound too boomy, boxy, or thick, which is why I'd lean towards EQ in this case.
My default setting on my MXR is to scoop the hell out of the 31 Hz, slightly scoop the 500 Hz, and slightly boost the 1 Khz, and work from there. It usually seems to do the trick. Also, if you don't have an OD, you could just leave it flat and turn up the level so it acts as a boost, so of the two, I'd take an EQ. Again, context dependent, yada yada yada. Cheers!