Really hard as I prefer the -ette ending if given the choice typically. But I think maybe just studying [name_m]Romeo[/name_m] and [name_f]Juliet[/name_f] a ton, I am just more familiar with the [name_f]Juliet[/name_f] spelling in this case. [name_f]Juliet[/name_f] just feels right to me whereas [name_f]Juliette[/name_f] feels too much. But again, I do usually choose the -ette ending so this is a one off.
[name_f]Juliet[/name_f]. [name_f]Juliette[/name_f] looks a little too frilly for me.
I vote [name_f]Juliet[/name_f], but only because it would be easier for everyone to spell that way since it’s the [name_m]Shakespeare[/name_m] way. Both are pretty. 
The,spelling difference translates to,differrnt emphasises for me, so it would depend on how you intend to say it.
Juliet: JEW lee yet
[name_f]Juliette[/name_f]: Jew lee YET
I prefer [name_f]Juliet[/name_f]. 
i much prefer [name_f]Juliette[/name_f]
Juliette
Juliette