not sure about sound between the size of turbos, i would think it would be the more boost the louder the sound but i am just guessing. as for if it is beneficial, i know this has been addressed before. the stock bypass valve it is equipped with from the factory is crap, and cars that are turbo in the US at least use these instead of atmospheric style BOVs like HKS etc. aren't used due to emissions related issues. any BOV that is not stock will hold boost better therefore improving performance, no matter what sized turbo it is. so in short, yes it is beneficial to replace the stock BPV with pretty much any choice BOV