External Quality factor

I want to measure external quality factor in ADS in 2 ways
1) Center frequency/bandwidth
2) by this formula==> Q=pi*freq*delay(S(1,1))

but the answers aren't same and have different..why?
which one is correct?

One possible reason is that the second formula doesn't distinguish between transmission delay and storage delay. You could arbitrarily add additional length of 50 Ohm TLine between the measurement port and the "Q" circuit.