yes, because dextrose is readily available. bananas I believe contain fructose, a more complex sugar molecule.
bananas also contain some fat.
i'm usually not hungry after a weight workout, so drinking my PWO carbs is just easier for me.
Maltodextrine also works as PWO carb source for glycogen and insulin spiking. main differences is that its not very sweet, while dextrose is very sweet...and malto won't stimulate the stomach to think you ate, while dextrose does.
some larger bodybuilders who need a lotta pwo carbs might feel bloated when they ingest a lot of dextrose, but usually won't if it was malto.