Back when it was just Yahoo as the best search engine around, it was kinda obvious about which email service would dominate, now there is loads out there to choose from.
Sometimes we choose a service based from friends and family using it, we choose that and then something else comes out better.
When it comes to knowing different languages that can do the same thing. U'd choose performance but computers are getting soo fast, that won't be a major problem. It sure does help to know how to improve your programs. But it don't help when there is so many languages out there. ASP, PHP, Ruby, perl.
My mind has been in a little frustration about it all and my thoughts on this "choice" issue is what makes us unique. What YOU like, which do you enjoy most? :D