For english-speaking users. Welcome!
What do you mean "more space"? 1 texture and 1 mesh(and it's lightweight thing), that's all. In case with pseudo 3d you need a lot of sprites to draw all positions. In true 3d you just rotate mesh in right position. There are many cases, when 3d makes a work simpler.
For example, in Warcraf3 you can't turn a camera, and you don't need it anyway, you're seeing everything.
When you do not see something, it's not 3D problem, it's level designers' problem.
You can set FOV to low, and you will see 3D as plane 2D.
But profit of 3D is in development of units and environment, as I said. You do not need to make a number of shots of every unit's position. Intead of it, you just can rotate the object in game into process.
Do you remember, we want to recolor Yog? Now it's very hard task, because we need paint every picture, one by one. In 3D we should paint just one texture.