A PS3 or 360 is significantly cheaper than buying a next gen console or gaming PC though...
If you already have a gaming PC, PS3/360 offer a vast library of games, something PS4 and Xbox One does not at the moment (so good luck if you want to play something else than Ryze and Forza 5, or Killzone Shadow's fall and Knack)
If you buy the 12GB PS3, be prepared to buy a larger HDD down the line (unlike the 360 you can use an off-the-shelf 2.5 inch drive) as the internal storage won't last long.
If you already have a PS3/360 but not a gaming PC, do consider one, the entry cost is higher but there's already a huge established library and frequent discounts.