From: Near Portland, OR
I have to disagree with you there, it was the most powerful sailing frigate (with her two sisters) ever built and it was much faster than any ship-of-the-line, and could while running away, tack and fire a salvo over and over, while the SotL would be unable to do the same without losing her. She also had 32 flippin' pounder guns. I would build a fleet of them and no SotLs, period.
Which is pretty much what the early USN did. They built as many frigates as they could afford, which unfortunately was not that many.
Another thing about the 32 pounders, any SotL's upper two gun decks would not have the range of the Constitution's guns and therefor the SotL would be technically outgunned.
One more thing about Ol' Ironsides. Beside being very fast, she was virtually armoured due to the design thickness of her upper hull. Thus Ol' Ironsides.
Rather than comparing her to a destroyer, I would compare her to a Klingon Bird of Prey. You could also say she was a Battlecruiser of her time.
I would consider a mere fighting sloop of war equivalent to a cruiser, anyhow.
While we're on the subject, I really, really like armed Brigantines. They would be equivalent to destroyers and I would build a bunch of them.
I'm not arguing with the power and utility of the early USN frigates. They were probably the most efficient fighting ships to their day, however they map to more modern ships. However, the thread is about BBs and battlecruisers have already been ruled out as the wrong class.
Another possible classification would be a pocket battleship, though mapping ships of sail to more modern ships is a bit tricky. The change in propulsion and the advent of armor on ships changed the way everything was done on ships to a point where the old classes only fit loosely at best.
WitP AE - Test team lead, programmer