Why Sinatra???

Not that Deano was a toad or anything but I think the "Betties" were, simply, more smitten with that oh-so-cute face from Hoboken.

I too prefer Sinatra by a wide margin; especially a young Sinatra. Although neither as much as Bennet, but that’s a different story. Sinatra’s phrasing was impeccable and considered by many singers and instrumentalists as “the standard”. The particular quality of their individual voices is a matter of personal taste and although I don’t particularly like the quality of Sinatra’s later in his career his sense of swing as well as phrasing was always pretty great; a true jazz singer. Dino’s voice had an inviting warmth not unlike Bennet’s, while Sinatra (especially later in his career) would sometimes convey for me the sense that he was doing the listener a favor by singing. Ted Gioia does a good of addressing some of this:

https://www.thedailybeast.com/just-how-good-a-singer-was-dean-martin

Sinatra was perceived as a serious musician and man, with his Mafia connections and all. Dean had the tipsy comic public image and often sang while in that character, which made people take his singing less seriously. Making movies with Jerry Lewis didn't help either.

Viridian....+1 on Sinatra. I never get tired of his voice, a real musical instrument and he was a great musician.  Deano, I like but not much of a musician IMO and Dean tends to sing in a schmaltzy way.