Well, as everyone previously stated, a realistic bank can easily do both while a robotic one is limited in it's abilities.
If you like the choppiness, you can just lower overlap values and tune angularly. If you like staticky noise, you can just add clarity-lowering flags. But a "robotic" vocal takes a lot more work to sound realistic, and in the end it's usually still kinda robotic.
A robotic voice sounds nice on certain songs, like electronic or pop ones and some of the more 2008 vocaloid original sounding type songs, but it doesn't work for a vast number of other genres and largely limits their cover range. Realistic voices can be tuned to suit a large range of songs.
Frankly, "robotic" to me kinda sounds like a gentle way to say poorly configured or badly recorded.
Usually the realisticness is in the tuning, but if a bank is totally incapable of sounding one way, then technically that counts as one of their shortcomings.
I guess the way I see it, realistic banks can do all the good things "robotic" banks can do, without any of the limitations of a robotic bank.