which multi-player style do you like better in shooter games?

[SpartanFX]

horizontal split screen ?or vertical split screen?

 

I like the horizental split screen more cause it gives me wider visibility(and abit less height which is not important),,,,and yet there are only few games done this way (i.e. Army of two )

 

why do most of the games have the vertical split screen?the view becomes really narrow and rather tiresome in the long-run game play