I think the design is just as important as the voice tbh. For example, between Cyber Diva and Avanna, I'd choose Cyber Diva because her design is better, which is saying alot since her box art is just a head lol, even though their voices are both pretty generic imo.
This matters less for english vocaloids, but because of oversaturation of a certain type of female vocals, the easiest way to stand out is the design. All of the most popular vocaloids (Miku, Gumi, Rin/Len, IA etc.) have iconic or at least memorable designs that are utilized in music videos, merch, etc. The only exception to this would be vflower, but I think that just speaks to how unique her voice. Vy1 and Vy2, who are both very high quality vbs imo, honestly are at a disadvantage because of their lack of a design imo. I mean, VY2's one hit solo hit uses his fan-mafe design.
TLDR: To me the design matters just as much as the voice. Oversaturated market, cute anime girls sell.
This matters less for english vocaloids, but because of oversaturation of a certain type of female vocals, the easiest way to stand out is the design. All of the most popular vocaloids (Miku, Gumi, Rin/Len, IA etc.) have iconic or at least memorable designs that are utilized in music videos, merch, etc. The only exception to this would be vflower, but I think that just speaks to how unique her voice. Vy1 and Vy2, who are both very high quality vbs imo, honestly are at a disadvantage because of their lack of a design imo. I mean, VY2's one hit solo hit uses his fan-mafe design.
TLDR: To me the design matters just as much as the voice. Oversaturated market, cute anime girls sell.