Yep, similar calibres, but more guns on the 1st rates. However, many Admirals and Post-Captains preffered the 2nd rate, as it gave up only a little in firepower, but was far more agile.
Than of course there was the massive Spanish 1st rate, the Santisima Trinidad, a four deck, first rate with 120 guns. Taken as a prize at Trafalgar, I think she was lost in the storm that blew up following the battle.