lens - Would the 40mm pancake or 50mm prime be better for street photography with a Canon APS-C camera?

I have a Canon EOS 600D, and I already have 18-55mm,55-250mm.

I plan to buy a new lens for street photography.

I already have picked out one of the following lenses:

1. 40mm STM(pan cake).


2. EF 50mm f/1.8.

Which is best one to buy for street photography use?