Those are difficult question but lets see if we can find some answers.

XB1 is heavier, but less dense and wider.

PS4 is lighter, but more dense and less wide but more aerodynamic.

Both with fall at the same rate, the gravitational constant, but the PS4 is more aerodynamic so it will have a higher terminal velocity then the XB1.

Given that the PS4 will have a higher terminal velocity, the PS4 will hit the ground first depending on how high both consoles are dropped from.

However, given that the XB1 is less dense, its extra weight is not significant enough to overcome to speed difference between the two, it has a higher likelyhood of surviving the fall.

So in other words, PS4 will hit first depending on how high the cliff is, and XB1 will be more likely to survive.

In regards to the swimming thing, PS4 would allow one to swim faster all other things constant because its aerodynamism would have less drag on the water. While the XB1 is more less dense, both aren't very buoyant, so weight and shape has a much greater bearing and the PS4 has the advantage in this regard.

XB1 also has greater chance of taking a bullet and working then the PS4, but clearly the most indestructable of consoles considering it has been tested to be the only thing that can escape a black hole unscathed and still play mario kart.