The number of complaints in the short-term in an unproven engine cannot usually be used to predict long-term reliability. There is no relationship between complaining owners of a new vehicle and long-term engine reliability unless there are engine failures (which there are not). If CR cannot figure that out and insert an appropriate disclaimer, they better stop putting out short-term reports.
I think the increased engine noise in the V6 comes from the timing chains, not from needing to work harder. There is very little difference between the performance of the two vehicles.