The X-factor 2 is actually cheaper then the origanal X. You can get the X-factor 2 RTR for 400 bucks at Hobbytron.com which is actually very cheap. The Mad Force on the other hand ... Is around 650 varies on dealer. But I own an X-factor and owned a Mad Force the are both great trucks but as lax stated the X-factor has unbelievable amount of low end torque, perfect for crawling. The Mad Force and X-factor don't lack any in speed. They're certainly not going to be up in the REVO/Maxx speeds though. I would pick the X-factor over the Mad Force though considering both their prices.
CHEERS, Lardman