Disagree, at least with respect to Behemoth & Colossus, the 2 capitals I'm most familiar with.
When testing a Behemoth found it took an eternity (unless I was flying it personally) to get into a firing position where it could use it's main guns &, even then, was very poor at using them effectively if the target was moving. Without those main guns it's relying on it's turrets & it simply has far fewer of them than the Colossus - 1 extra L turret on Behemoth does not make up for having 8 fewer M turrets than Colossus. That's before you dock a bunch of M ships on the Colossus (I favour Peregrines) to provide up to an additional 16 M turrets, though I find 12 is more than enough & leaves me a free docking bay for my personal ship.
This is precisely what I've been using my Colossus for. It has had no difficulty at all dealing with 2-3 Xenon destroyers, even simultaneously - it simply out-guns them. On some occasions there have been many more than that in sector & still no serious problems. It's the main reason I got it - Colossus kills the capitals (their hulls are tediously thick to deal with any other way), while I go after the fighters. Quite often I'm struggling much more than the Colossus on these engagements & frequently have to run away to let my shields recharge if there's more than half a dozen or so on my tail. These days have no concerns at all about actually losing the Colossus, even on the rare occasions when it's shields have failed it has proved really quite resilient, much more so than I was expecting (certainly when compared to X3 equivalents, which were pretty much doomed as soon as their shields went down). Worst that's happened so far was having to repair 18% of the hull, 1 engine & a main shield. It's a very tough ship.