I really think Tangrowth is better than Amoonguss and walls a large portion of OU. It can take outrages, earthquakes and stone edges much better than the Mushroom. Leech Seed/Earthquake are nice moves to have to wear down Jirachi or Heatran, or for stalling out Pokemon such as bulk up Conkeldurr. I guess it all depends on weather you want a special or physical wall.