There are a few differences between the shorty and standard length silencers depending on the model. Remember though, with 2-stroke tuning what you might consider a slight/small change has the potential of being a lot bigger than one might think.
With the shorter length can and altered core size, we decrease the amount of backpressure in the muffler, which on a 2-stroke will increase throttle response and low to midrange power. Some models may see a slight decrease in over-rev though with the Shorty.