Horizontal or Vertical Reservoir

[PumaXCS]

I will be going tube res as my case won't have a 5.25 bay and I think they don't look as good. Trying to plan my loop before I get the case and keep things a symmetrical as possible. The case is a custom mod, 3 intakes and exhaust out the top with a rotated motherboard tray. Two intakes from the sides, and bottom and passively exhaust out the top. My options right now is to have two vertical res at either side, which seems excessive, or a single horizontal across the bottom. Which would look/work better? I know adding extra coolant lowers temps slightly but I'm more so interested in how a horizontal res drains more than anything. 

 

While I'm here, can any reservoir be made to work any direction or do I need to get a horizontal res?

[Denned]

As long as Gravity can do it's thing to move water down to the pump, then it shouldn't matter what way it's oriented.