My opinion doesn't actually count unless it's shared. Whose favorite singing character... and I'm only counting those who was voiced by one speaking actor/actress and one who did the singing for that actor/actress. No way will any who did both voices count. Whether a character's singing is done aloud or in his/her head doesn't matter, nor does whether he/she is a hero/heroine or a villain/villainess, or even neutral. If needed, I'll add more rows.

Character Film or TV Series Speaking Voice Singing Voice
Fa Mulan Mulan & its sequel Ming-Na Lea Salonga
Jasmine Aladdin & sequels & series Linda Larkin Lea Salonga (first film); Liz Callaway (sequels)
Kiara The Lion King II: Simba's Pide Neve Campbell Liz Callaway
Nala The Lion King Moira Kelly Sally Dworsky
Pocahontas Pocahontas & sequel Irene Bedard Judy Kuhn
Ferb Phineas and Ferb Thomas Sangster Danny Jacob
Maid Marian Robin Hood Monica Evans Nancy Adams
Simba The Lion King

Jonathan Taylor Thomas (juvenile) (first film);

Matt Weinberg (juvenile) (midquel)

Matthew Broderick (adult)

Jason Weaver (juvenile);

Joseph Williams (adult) (first film);

Cam Clarke (adult) (second film)