Not sex link- they dont have feathered legs. Not marans- he has yellow skin.
Barred rock cross/mix is a good guess as BR are extremely common. Cross of BR and breed with heavy leg feathering would be reasonable guess.. like giant cochin, brahma....
due to not having any other color present on hackles/saddles, the heavy feathers on legs, long loose fluff on rear plus seems to have extra sickles on tail, I'd personally guess barred rock crossed with black giant cochin. iirc, cochins also have yellow skin, which is recessive so this cross would be guaranteed to throw all yellow skin, which this rooster has as evidenced by yellow legs.
He's 'darker' than your old rooster because this guy is not pure for the barring gene. It has a dose effect- meaning roosters 'pure' for barring will be lighter than 'not pure for barring' roosters and hens(because it is also sex linked, which means hens are able to have only one copy of barring or none at all... unlike roosters which can have either double dose, single dose or none)