I'll take a masterful actor like Gyllenhaal who, by all accounts, can more than hold his own in the singing department than someone like D'Arcy James whom I believe lacks the charisma and presence necessary to realize what's ultimately (on paper, anyways) a hard-to-like protagonist. As Ljay said, Sondheim himself has often opted for actors who can sing.
I only wish that any talks of a full production actually materialized, which I think is rather unlikely. It'd be so wonderful to see an event production of this masterpiece headlined by a huge star like Jake Gyllenhaal. How exciting would that be!
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"