The Decados dread probably throws more nastiness than any other ship in the game, but only within 15" range. If your enemy plays keep-away for the first couple of turns, you can have real problems, especially if they score a few key crits during that time. Once you get those meson turrets firing you're a positive menace, though - even a few Devastating+1 crits will let you beat practically any other dread in short order. You may need some help from the rest of the fleet to drop an enemy dread's shields, though - pity to waste meson hits on a shield, especially with no Burn-Out.
The Hawkwood dread is nearly as scary but its Precise crits tend to be scattered all over the place, reducing the odds of getting to the really brutal (stage 4+) crits. Scout guidance gives it excellent accuracy, though - rerolling on a heavy blaster turret is nasty, but doing it on 5 heavy lasers is just sick.
Hazat's dread is a weak sister compared to the others without major Scout guidance, and even then it's just not getting the average number of crits they will - and crits decide dread duels most of the time. OTOH, it does have a solid range edge over the Decados design, and slightly outperforms the Hawkwood dread for raw damage (assuming Scout parity). It's also fast enough to hypothetically catch and board a Hawkwood dread, at least if it can avoid too many engine crits - but getting to board anything with a Lumbering ship is a chore.