Effective VCA complements sort of REQUIRE different VCAs...since you can't really use an exponential (for audio, primarily) VCA to control modulation signal amplitudes. You've basically got those two types: linear, in which voltage relationships are maintained, and exponential, where the signal follows our psychoacoustic exponential hearing profile. Also, most of the latter tend to be AC-coupled and won't pass a signal below a certain frequency, generally in the subsonic range. Linear VCAs, though, tend to be DC-coupled, which allows modulation and other subsonic signals to be processed by the VCA.
Then there's the Veils and the Intellijel Quad VCA. These are DC-coupled...but have a curve control that lets them work on a smooth continuum between linear and exponential response. Far as I'm concerned, these (and designs based on the Veils topology) are the "standard" as long as you have the space for them. Now, you see me (and others) using the Happy Nerding 3xVCA for modulation VCAs...and these are perfect for that in terms of space needed (6 hp) vs amenities offered (three linear VCAs) as you probably won't use those for audio. So when you have an obvious application that requires something other than that sweepable curve, sure, use different VCAs.