Here's my Top 11 rank for my favorite Vocaloids and UTAUloids put together (As of May 20, 2016):

1. Kagamine Rin
2. Kagamine Len
3. Hatsune Miku
4. Momone Momo
5. Megurine Luka
6. Megpoid Gumi
7. Kasane Teto
8. IA
9. Kamui Gakupo
10. KAITO
11. MEIKO

My pick is at the bottom but I will not be influenced by those popular one. I pick him because his voice is very unique. His voice, before being edited, would be an averagely deep voice, but now that it's been edited, it's high pitch and the high and deep collides, creating volume to the voice which makes it seem like a true Vocaloid to me, while the MOST of the other voices, they're just becoming more high-pitched after the editing. I'm not saying none other Vocaloid have the same voice trait as Kaito but I'm just saying that he also stands out to me because of his "character traits" in my imagination. I imagine him as a person who hides a scar behind a smile because, for most songs, he's one of those generic dense, and always smiling. Those character traits are overused because Vocaloid IS a very old thing so his "character traits" are pretty generic but- do I even need a reason as to why he is better than the rest? But remember, this is ONLY, ONLY my opinion.

Hatsune Miku is #1 best Vocaloid.