From practical viewpoint, I'd have to say Junkers 88, because its very wide range of capabilities, performance and of course how we Finns used it historically, too. The ability to level bomb or dive bomb, depending on target, was very useful and the extremerely good accuracy was put into good use historically. I just cannot forget the descriptions of the Finnish vets, how 500/1000 kg bombs caused destruction in Russian armor concentrations - or how a 1000 KG bomb completely destroyed a Soviet transport full of soldiers, trying to make naval landing behind Finnish lines. Cruel, yet efficient.
But on the other hand, nothign just beats Heinkel 177 A-4/A-5, how devastating heavy bomber it was, how well armed, how well they fought against Soviets, how efficient they were in naval recon and interdiction in the Atlantic... Yet, how the plane achieved its potential too late.