5 deg bank is a certification limit available to be used to determine Vmc. It's not a performance related specification. AoB can be used in lieu of or, more importantly, in addition to rudder to counter yaw - effectively reducing Vmc. Because up to 5 deg AoB is allowable under the certification rules available then all manufacturers of which I'm aware use it to minimise the certification value for Vmc.
Best performance will occur when there is zero sideslip. If you use rudder exclusively (ie no Aob) to counter asymmetric yaw then there will be sideslip. If you use AoB exclusively (ie no rudder) to counter asymmetric yaw then there will also be sideslip but from the opposite direction. Somewhere between those two extremes is a zero sideslip condition. As it happens, the crossover point ie zero sideslip occurs at ~2-3 deg AoB.
So, in the world of desperation : If you need more control authority to control asymmetric yaw and reducing power/pitching down isn't an option for some reason you could use more AoB that the 5 deg limit.
If you need every last last ft/min you can wring from the a/c then fly at ~2-3 deg AoB.
If both control & performance are acceptable then fly at 0 deg AoB. It's a bit more comfortable & performance is about the same as at 5 deg and you have a nice big 0 deg roll index to point at. So why bother at 5 deg? You have an examiner on board, of course!
