All these vendors organize their offerings by product lines, which should make it easier to buy, since you can simply (in theory) go directly to the product lines targeting small and medium-size business customers.
In fact, some vendors have several product lines for business buyers, and you’ll find a distinct lack of clarity as to the differences among said product lines, other than that one line tends to cost more or less than another line, but not consistently even in that. Other vendors seem reluctant to state clearly the intentions of each brand name — every single system, it seems, is targeted at buyers who want flexibility, quality, and value. (I am still looking for that other product line — you know, the one aimed at buyers who prefer rigidity, frangibility, and high prices.)
In an attempt to figure out what’s what, we studied the product lines and then, defeated, talked to the product marketing managers of the various brands. But that didn’t always help. So here is our interpretation of what we found out by studying the vendor sites and literature, consulting with our user sources, and shopping the sites ourselves. (Our interpretation may differ slightly from what the vendor marketing people thought they were telling us.)