Ah, now I get it.. I thought you would be looking for something more technical or official I guess lol. Anyhow..
Horizontal - This way would be very efficient at hitting vital points on the body. Starting from the top, slashing horizontally at the eyes, throat, abdomen, back of the thigh, or Achilles tendon are all points that could be fatal or lead to a situation in which death is immanent. After you deliver a horizontal blow, your arms will be across your body and your shoulders slightly turned inward. If you were to flip your sword so the blade is facing the other direction, all you would have to do is rotate back to your original stance and you would be ready for a quick counter. This swing can be easily blocked by a vertical block.
Vertical - This swing is one that is used when one is trying to exert a lot of power onto one blow, as when you are trying to overpower your opponent. The main problem that I see with it, is while you are doing it, usually you would have to raise your arms above your head. This would lead to an opening at your abdomen, chest, and throat areas, so this is something to be weary of before doing it. I would say that this is best utilized when you have a height advantage over your opponent. This is because, this places the opening lower, and at a non-fatal point in the body. This swing is easily blocked by a horizontal block.
Thrust - If used correctly, this swing could either be your victory tool, or your doom. It is very quick, and a precise swordsman could pinpoint the exact area that he wants to stab. Where most swings focus on the surface area of the arc of the swing, this one focuses on one point, so instead of a slashing effect, you have an impaling effect. Now, this is good in that it is harder to block, but that the same time, it is easier to avoid. It damages less overall areas, but does more damage to areas that it does hit. If this is avoided, or if you hit a non-vital area and get stuck, you are open to attacks from every angle, so this one is very risky.
Diagonal - This one combines the horizontal and vertical swings in a way. You retain the power of the vertical swing, but don't remain as open. You have more vital spot choices than the vertical swing, like the horizontal. The interesting thing that I am seeing is that a vertical block would put my blade down, while a horizontal block, would lead it outward. This could create an opening for either person in any situation. This swing would be perfectly blocked by a block of equal, but opposite diagonal angle.