Both saws share the same crank shaft/bottom end. However, the 357xp has stuffers on the crank that moves the peak power higher in the rpm range. They also have a smaller displacement cylinder, but better port timing that favors the higher rpm power range. The 359 has a larger displacement, but much more tame port timing and a very broad power range that comes off as "sluggish." Swapping "stock for stock" putting the 357xp top end on on the 359 bottom with no stuffers, broadens the power range of the 357xp cylinder and makes it less "peaky." The 357xp cylinder also has better port layout and a true quad port transfer design, so it "punches up" the 359 saw a bit. Keeping the added displacement of the 359 top end is favorable in my eyes, if porting is involved. Only one man's opinion of course. That being said, either cylinder will make for a GREAT runner once ported.