I start immediately with the answer without beating about the bush: horizontal or vertical does not change anything for the mere purpose of cushioning. The cushioning gives it the overall cushioning pattern, not the position of the damper itself.
In recent years, shock absorbing schemes with horizontal shock absorbers have been going a lot because it brings advantages: the use of a double bottle cage (on a bike marathon is an important feature and in fact it is also for this reason that it is used a lot on bikes with a "pedaling" propensity. ) and the possibility of lowering the center of gravity of the bike (its geometric value is called standover).
In conclusion, it is necessary to look at the shock absorbing scheme as a whole and I refer you to some interesting links where we study some of them. Be careful, you could lose your mind on these topics.
PS: But what if the shock absorber was oblique? 🙂 If you have been careful you should have the answer.
