He's probably telling you what's easiest or most profitable for him. Check out images on line and in magazines with modern bathrooms. I would think a sharp square edge would look more current than a bull-nose edge. Either way you could achieve a modern look if it's done right. This has no baseboard just tile on tile.

I've gone through this myself. I was advised by my tile installer that it is easier to remove wood baseboard, should I ever decide to install wall tile on the bathroom walls, than to go with a bullnose tile baseboard. I have one bathroom with the bullnose tile and two with a wood baseboard. I prefer the look of the wood baseboard. I think you should go with what you like. I don't think one way is more modern than the other. What's going to determine how modern or contemporary the interior design will be the overall look of the room, the tile choices, the color choices, cabinet choices.