[Google]

You can use a keyboard and mouse on a PS3 or Xbox, you just need some sort of an adapter. However that's the thing, it's basically going to be just like a PC without customizability, it'll be around the same price as a low-range pc specification, but it'll be a little better than your average gaming PC due to bespoke component.

In my opinion, I would rather just either get a console, or a PC; why go in the middle?

because you will have both? - less space. or for people who are travelling a lot and love playing.