I have doubleshots from various keyboards from 1977 - 2013, and I don't really see the "dyesub is less precise" issue. My "imprecise" dyesubs are from ancient IBM keyboards. I have IBM dyesubs that look excellent. Modern imsto dyesubs are very clear.
It's no secret that I prefer PBT. Dyesubs offer several things doubleshots don't, specifically multiple colours (multicoloured doubleshots are called tripleshots or quadruple shots, depending on the exact process involved and the number of injection moulds used) as well as gradients. Of course the whole "darker colours" issue hasn't been addressed yet. You could dyesub all of a pbt keycap except the legend.
As far as material differences between ABS and PBT, PBT is harder, more corrosion resistant and more brittle. The brittleness is usually more of a factor in shipping keycaps, and the other aspects are generally superior for the purpose of keycap use. Many people report PBT keycaps not getting shiny as fast. PBT is also more expensive.
Now: about legends. Properly made dyesubs can be just as clear as ABS doubleshots. I have seen doubleshots where the legend is not as "crisp" as what some people evidently think. Because of this,a nd other reasons, I prefer dyesub PBT. How fortunate for me that it is also available for my favourite keyswitch technology: buckling spring.
Nevertheless, as ABS and PBT are different materials, ABS and doubleshot ABS have their place. While I might prefer PBT in general, ABS doubleshots are cheaper, easier to get, are in general an excellent keycap making technology, and have a different "feel" that others might prefer.
Me, I want doubleshot POM