Personal preference always rules in the end. However, you might try thinking through the definition of "better suited." Not all mountain bikes have attachment points for front fenders. If your cruiser does, it might be better suited. If you have hills on the trip, the mountain bike might be better suited. Do you like to sit up in traffic--cruiser. Are you habitually running late in the morning--mountain bike. Is the more bent-over position less comfortable--cruiser. Are there any really bad stretches of road--mountain bike. Do you park in a high-theft area? Do you stop for groceries on the way home? Will you be riding in the winter? It goes on and on, which is part of the fun.