Eric,

I do have several (even several 150mm) lenses from various manufacturers and from four decades. Both Schneider and Rodenstock do have gems in their lines (e.g. the discontinued Apo-Rodagon 4/90 or the new Apo-Componon 2,8/40), but most of their lenses perform equal in practice (comparing members of equal categories). Even if your enlarger is perfectly aligned (which would be essential to even tell any differences between a four and a six element lens), you will hardly notice any differences between a Componon-S 5,6/150 and a Rodagon 5,6/150. It is even hard to tell the difference between a Rodagon from the 60ís to one from the 80ís as long as both are single coated. Multicoated lenses naturally do have better contrast transfer (up to one grade for huge prints). If you plan to buy one second hand, go for a multicoated lens (which are hard to find, except for the APO-Versions which usually are multicoated). The Schneider EL-lenses do come in two different barrels. The BLV-version does have a lever to open and close the aperture to the preset f-stop. This is convenient and an advantage of the Schneider over the Rodenstock.
Schneider has two lines of six element EL-lenses (three if you want to include the G-Claron process lens): the Componon and the Componon-S. They are different calculations (the Componon is 1-2-2-1 and the Componon-S is 2-1-1-2). The Componon-S will perform slightly better outside the recommended magnification ratios (2-20).