In reply to FF Scala vs. FF Yoga (serif):
I suppose shooting the breeze discussing conceptual approaches to typeface design may have some benefit as a pleasant diversion, but rather little practical consequence. On the other hand, perhaps being impractical is what makes some experiences pleasant, since they serve no purpose other than amusement, which is an excellent—if useless—exercise in itself.
In other words, a simple appreciation that something works is often preferable to knowing why something works. The article Hrant cited provides a lot of rationalizations, intended primarily to convince us to buying the font makes sense—and who doesn’t want to think of themselves as eminently practical and world-wise?
Bottom line: Yoga shows a strong Eric Gill influence, and the typefaces are similar in that the designers appear to have habitual ways of rendering certain characters. In other words, siblings sometimes look alike, no matter who’s their daddy.