the bearing will only fit on the crank one way, and then you insert it into the halves.
referencing your picture, you want that face of the oil seal facing out.
the polini one may be different, but im sure it will actually hold pressure either way. this has been discussed at length but none of the threads are worth reading since a conclusion is never made.
but like harvey says, what i go by is removal. when you put it in like that, you can tap the seal out with a flathead when its time for replacing. you rest the flathead on the metal lip of the seal and tap tap tap. if you were to install it the other way, well there's no easy way to get it out. surgical use of a dremel and other picking tools may be necessary.
oh and plus, thats how the seals come stock.