Goten and Trunks can't progress that much considering the fact they got lazy and has some other activities to do, they ain't making it to Vegito possibly even Boohan.
I don't know if Goten/Trunks got stronger or weaker, there's really not much to go by other than Goku and Vegeta indicating they slacked off and that Goten couldn't beat Mr.Boo. I'm going with Vegetto on this one.