What is faster a Yamaha banshee 350 or Yamaha yzf 450?

They are very different from each other. Banshees are a 2-stroke motor and yfz450 is a 4-stroke. Both are fast and both can be faster with modifications, however, you can take it much further (with lots of money!) on a banshee. Up to around 130 horse on a drag bike. 4 strokes are easier to ride though, because they make power and torque through the entire rpm range. 2 strokes will bog until you get into its "power band" where it will then rip your arms off. Stock banshees are not this way but like I said-money talks!