The kick back would be roughly the same from NAB or other ba...

The kick back would be roughly the same from NAB or other banks. Broker might have a better relationship with the NAB BDM possibly which in theory would probably mean a better experience for you.
For what it's worth, $National Australia Bank Ltd(NAB.AU)$ are pretty great in terms of approval times and their processes - but are definitely not price leaders in terms of rates. $Burgundy Diamond Mines Ltd(BDM.AU)$