They arw two very different turbos mate. The 35 if you've not built your motor and only want to spend 2k max. The 42 8f your budget is 5k and a built motor. The 42 will be about 400 - 500 rpm more laggier than the 35. Ethanol fixes a lot if the lag these days though. Best you set yourself a goal and budget select the right turbo from there.