I own a Mammoth ST and would have to say for hardcore bashing go with the Savage. The ST still uses the regular Mammoth arms and Bigair's (
http://www.bigairproducts.com/) aluminum ones will set you back 100.00+ but they will not break. If you are willing to buy the arms I would say go for the ST.
Hobby people sells all of the hop ups that you will ever need.
rolland