Don't do fiberglass in any area. If you want no grout, do acrylic instead. Sterling is Kohler's budget line and offers good quality.

Fiberglass surrounds are harder to clean than ceramic or porcelain tiles IMHO. We have done curbless glass tiled floors. In those cases, the tiles were 1" or less so the grout provides the traction. Use a single component grout for stain free, color fast lifetime of use.

You could do a Kohler cast iron shower pan and tile the walls.

I like mayflowers suggestion.

I have a Swanstone shower surround and it is amazing easy to keep clean, and looks like solid surface material.

We lived in a house with a fiberglass tub and surround. I hate it. Felt flimsy to lean on. Hard to get hard water calcium build up off it.. Current house we have tub with tile walls, fiberglass pan with tile walls, and tiled floors and walls. We've not had any trouble maintain any of them so far. The old master shower sucked but it was old and leaking. There was also no fan so the shower never dried out like it should. Regular cleaning and a good fan go along ways to keep tile mold free.