It depends really. Depends on my mood, or what vibe it gives off.

I tend to prefer most without vocals.

Vocals! Usually female voices are really getting to me....

It depends on what kind of Electronica and on what kind of vocals.
I mean, if we're talking bout a soulful / funny / crazy track, powerful singers and rappers are OK.
But, if we're talking bout a deep and introspective track, the best would be the Dub Poetry and Spoken Word kind of vocals. Traditional singers would compromise the track's depth.

Really depends on the genre.

No vocals ~80% of the time.

Yep, no vocals here. I think it's the fact that electronic music has a certain audiophiliac feel to it that's in sharp contrast to a human voice. If there are to be vocals, let them be autotuned or otherwise heavily engineered.

Right, most of the time when I'm listening to electronic music it's because I want to hear something alien, something that wasn't produced through conventional methods with traditional instruments, new sounds that are only possible through electronics and clever software. Of course there are more pop oriented groups where vocals are suitable, first recent group that comes to mind is CHVRCHES, but I think the majority of electronic music (meaning everything outside of dance music) is more often than not about using technology to transcend the limitations of traditional instruments rather than designing a simple foundation to sing over. But again, vocals certainly have their place even in experimental electronic music if they're sufficiently manipulated.

1000% agree.

I think sampled vocals work best with electronic music, particularly when they sound amorphous and add an otherworldly feel.