To be taken with a pinch of salt, for the simple reason that I've not tried these out on the tabletop yet - but we know Imperial Fists will get additional bolter hits on unmodified 6's in the new Codex.
With that in mind, I've got a unit of Centurion Devastators with heavy bolters.
Of course any decision like this hinges a lot on the rest of your list, and I'll be running a couple of Lt's and a Captain in that list to make the most of those 6's. Your characters might be tied up elsewhere?
It all comes down to what role you want the slot to play, and what you've covered so far already includes some anti-tank in the Eradicators and Repulsors, and some anti-horde in the Aggressors. You might not want the redundancy on anti-horde if you've already got a lot of Intercessors too (and if you haven't - what are you waiting for?).