One problem with the "perfect well approach" is that people see the result and will immediately dismiss it, because it is completely unrealistic - it's really hard to get people on board if you use that as a benchmark - I know that's not the point but this is how ppl react to it in my experience (especially if the performance engineer is younger) ... I find the "best in class" approach better in that regard, since "people have done that" makes it less academical and team members are more willing to listen - because everyone wants to know how it was done ... and that is a good starting point ... but of course the "best in class" approach may not reveal certain improvement potential.
One problem with the "perfect well approach" is that people see the result and will immediately dismiss it, because it is completely unrealistic - it's really hard to get people on board if you use that as a benchmark - I know that's not the point but this is how ppl react to it in my experience (especially if the performance engineer is younger) ... I find the "best in class" approach better in that regard, since "people have done that" makes it less academical and team members are more willing to listen - because everyone wants to know how it was done ... and that is a good starting point ... but of course the "best in class" approach may not reveal certain improvement potential.