I am noticing that at the same RC input being commanded (MOTB also the same in logs), the RCOU in stabilize is consistently lower in 4.6.3. Did anything change in the motor output in Copter 4.6 that would cause such a change? It is consistently 8-10% lower (RCOU) in 4.6 compared to 4.5 for the same RCIN and MOTB.
It would be better to provide logs of test flights with both firmware versions, so that we can test possible hypotheses.