Maybe it's wrong, but according to the coriolis links I provided, when setting max fuel and no cargo the courier is showing superior degrees per second on all axis at both boosting and not boosting at all pip settings.Whilst the Courier is a great ship, you're not correct on the manueverability point.
Courier isn't anywhere close to as maneuverable as the viper, the second the boost gets hit. Given that both need to boost to get the speed up, viper is massively more agile than courier at speed due to its great boost profile.
This doesn't take away from the great utility of the courier. But it has a junk boost and lacks high speed agility as a result.
Definitely fastest multirole tho, by far. Its a good ship.
Edit : its way better than imp Eagle too. That is truly a ship with suck level agility.