There's another thread where I went more in depth over the differences, but to keep it simple, there's really no difference flavor wise from verticals to horizontals, but the functionality usually improves. Verticals will prevent spitback from going up the DT/Chuff, instead aiming it towards the Cap and out the AFC. Verticals will also allow you to easily drip down the DT/Chuff and onto the wick directly, and excess juice will run down the coil and into the juice well, as opposed to just sitting on the coil and causing spitback.