A question I would ask myself is, "Why is the engine so clean in the first place? What was it like before? Was it leaking oil everywhere and he just cleaned it up to make it look 'better'?" Those questions could be shit, but you never know, something could've gone wrong and he just cleaned the engine to hide that problem.
I would just purchase the car that's in better condition overall.
Goodluck with your purchase, I would still go for the white one. I just like white