I say go for the GST. I have a buddy with the savage, and it's handling is like a pig. I mean, it's fun and all, but handling wise, it isn't too good.
The GST/nemesis, though, and very good handling. If getting second in Monster truck and the Nats with a stock Nemesis isn't impressive, then I don't know what is. If you're just bashing though, either will be fine. You should also look at the type of radio to get with the truck. The Nemesis has the Airtronics MX-3 FM, and the Savage has a cheaper, HPI controller. The Airtronics controller has all of the essencial features, and plenty of extra. The GST has the Skyion DSX radio, and it's still a great RTR radio with plenty of features.
CEN's customer service is also second to none..best one out there. They can help you with any problem you have, and new upgrades and fixes are being designed and made all the time.
Just look at this
http://www.rcuniverse.com/forum/m_7222959/tm.htm
He's had a great time with his truck!