I am not a masonite lover, although, I know it is used a lot and paints up very nicely. To me, I just do not like the feel, so I would go for the poplar. I am sure you can pick another type of wood too, if thats what you would prefer, or any profile you prefer.

Solid core doors would be my choice. I currently have hollow core masonite doors and slowly replacing them with solid core MDF doors. I did not get wood doors because I would be painting my doors. I would get a paintable wood over a hollow core masonite door.

Good luck!

Solid core function outweighs design for me, but I agree that I would look for less expense paint grade solid wood if you plan to paint them.