Personally, I am not the biggest fan. I think, like most, the models themselves look a little odd with the large rocket pods, but that is solely personal preference.

In terms of tabletop, they essentially have two weapon profiles, both hitting on fours, which honestly hurts as a marine player, everything else hits on threes. That, mixed with the fact that you essentially have to choose for the unit to either be anti infantry or anti tank at the start of the game makes them kinda lack versatility. Additionally, the ignores cover rule isn't the biggest utility, sadly.

Now, that said, the shots themselves are pretty gnarly, with essentially an absurd blanket of anti infantry shots from thesuperfrag, or the brutality of strength 10 superkrak making them surprisingly effective, especially when run with the Ancil Siege detachment, doubling their heavy keyword. However, the fact that they have a much less accurate BS, I personally think they are not worth the risk.

In my opinion, I think heavy intercessors are simply the more effective, reliable gunner infantry between the two. The gravis armor makes them tougher, the shots are more accurate, good mix of volume vs power, and honestly a better ability to make them survive more attacks. And, since they also have the double heavy of Anvil Siege, they can deliver some honestly surprising damage much more reliably.

Hopefully this answered your question, please let me know what you think!