In article , kgarland@vt.edu says...

>What is the significance of knowing how many groups / how many elements
>when comparing lenses?

Not a heck of a lot. When there have been several offerings with
the same focal-lengths and speed by the same company, it can be useful
for identification (and the higher number of elements/groups version
will tend to be better within a line). When you cross lines, one or
two elements/groups differences may be meaningless, especially on more complex designs (a better design, or one with aspheric elements, may
have fewer elements than another lens of about equal, or inferior,
optical performance). In some lenses, a "floating" element can be an
advantage for maintaining good performance over a wide focus range
(retrofocus wide-angles, macro lenses, and some short tele designs
can benefit from these).
Hope This Helps