Yahoomail is best it offers sophisticated ajax based site than gmail.It loads fine even in slow dial up gprs connection.Whereas in gmail I can't use standard mail, I have to use basic html version.In yahoo mail homepage I get news, weather and mail on single place.Yahoo has signed contracts with mobile manufacturers and operators.So I am always connected with my contacts.Its mobile site is better than gmail too.
Although I use both gmail and yahoo and if it was allowed to vote for multiple options, then I would have selected both of them.