Sporty had the best voice (and one of the two best solo albums in Northern Star (the other being Emma's Free Me)), and her wardrobe seemed like the most comfortable.
Sporty's voice always sounded shrill and sharp to me (especially in her live performances with the group), but neither of them were strong vocalists, so she won in the vocals categories by default.
Vocally, I always preferred Scary>Sporty>Baby>Posh>Geri