cd storage horizontal or vertical?

All the cd storage racks I see for sale hold them horizontally. I have read that the best way to keep them is vertical in the original holders. I am quickly running out of room and need a way to store them in a neat way, what is your experience?
There should be no reason (mechanically or sonically) to store them one way or the other. Well, One reason..... You can read them more easily if they are horizontal.

The highest density, most convenient, inobtrusive storage is in a drawer, vertically, in rows front to back so you can..... yes, you guessed it!!! Read the Lable.