It doesn't matter.

Though there is a theory about which way would be better. Theoretically, having the open side of the pin facing the intake would slightly increase the crankcase volume, reducing crankcase compression. So, theoretically it should go the other way, open side facing the exhaust. In practice, it really doesn't seem to matter.

I have sometimes thought about another option. If the pin had a small, perpendicular oil hole and the open side faced the intake, that might improve lubrication to the upper rod bearing. Then again, maybe not. The pressure waves in there can do weird things