I'm trying to think of examples, and the answer I got was that it's mainly the Onslaught. Non-capitals tend to have larger mounts on the hardpoints, and that's their advantage. (E.g. Dominator, Sunder, Hyperion. Eagle's an exception but the hardpoints are still different than the turrets. Also Wyvern's point is good - +OP for hardpoints can be baked into base OP.) The Conquest, Odyssey, Atlas and Astral don't have much in hardpoints.
So here's the thing. When you turn the Paragon forward to bring its hardpoints to bear, you don't move its large turrets out of their firing arc. On the Onslaught, you do. On the contrary, the Paragon's large turrets overlap mainly forward.
On the Onslaught you trade one large turret for two hard-to-aim large hardpoints, plus a couple medium mounts. Which doesn't sound that bad now that I write it down, so I think the problem is in getting it turned around and in the fact there's a dead zone between the side turret and the hardpoints. There's a spot where you're trading the heavy turret for one hard point and maybe some medium turrets.
And I don't know about you guys, but if I ever need to turn the Onslaught, my enemy tends to get stuck in that dead zone.
As a result I've found an extremely effective Onslaught build that strips the hardpoints entirely.
Come to think, I know why stuff gets stuck in the dead zone, too. If you have exactly one opponent, you can see them coming and line up. If you have a second opponent, it is impossible. While you're turning to meet them, those hardpoints are dead weight. So instead I planned around disabling the opponent before they could turn to meet me, and it works great.
