Selena actually has the stronger voice, but you can only witness that in acoustic performances when she is sitting down. Hilary has a slightly breathier voice, kinda like a less sexier and nasal version of Britney Spears, but it works well for her songs and her performances. Hilary has the better breath control and I'd say slightly more consistent performances, so I'll go with Hilary.
You should have done a poll for this.
