"...(recording the vocal simultaneously onto two tracks...)"
That might be interesting. Especially if you used two mics with different tonal colors, or processed the tracks differently (tweak the EQ so one emphasizes different frequencies than the other, for example). Even identical tracks panned hard left & hard right can sound more "full" than a single track panned center.
Worth experimenting with, but definitely listen to the results and be prepared to try a few different things before you get the sound "just right". Marion, I'm guessing you're looking for a sound that is "natural" rather than obviously processed? That calls for a bit of subtlety with whatever you do. If your recording engineer has a clear understanding what you want, and if he/she is both skilled & artistic, he can probably get there one way or another.