What happens when a PWM controller is over amped? Zap = bad?
MPPT overpaneling can be very benefecial. It can allow maximum MPPT power over extended hours surrounding noonish. Most systems will not reach their maximum at 1:00 on a clear summer day in the south, let alone in the north. So who cares if there is amp clipping for a few minutes at 1:00 vs say increased battery amps for say +- 2 hours if one chooses to over panel?
And a oversized PWM controller will not see and real cost/performance benefit of 25% oversizing. But they do cost less.