Usually the grout joints (space between the tiles) determine use of unsanded vs. sanded grout. Wider joints require sanded grout (which would be "grittier" given the added sand), while tighter joints require unsanded grout, which would be smooth.

For our kitchen backsplash (glass tile, mesh-mounted mosaic), our tile guy mixed sanded and unsanded grout (I have the ratio written down somewhere). It has a smoother appearance than the fully sanded grout used with the border/accent tile in our MB.

You can ask your tile guy if your tile will allow for tighter joints, and then use unsanded grout (some tiles have their own "built-in" spacers, so they cannot be installed any closer to the next tile than these lugs or spacers will allow).

Barring that, you can ask if he can do a mix of sanded and unsanded grout, as our guy did on our backsplash.

(we might have a mix of grout types on the shower surround in our guest bathroom as well, but I don't remember)