We should probably go with max turbine inlet operating temperature where you get the most efficiency
The temps are starting to plateau between advanced engines in the field. His list list would certainly be a good examples. I've seen the charts for what he's looking for, so maybe google would help
Agree that EGT is not a good measure since by that time your turbine efficiency has massaged the temps downward quite a bit. EGT is easy to measure and a pointer at engine health, but by itself doesn't mean much in range.