I started on electric because my brother already had one he didn't use. I probably would have anyway though. If I had started on acoustic I really doubt I would still be playing honestly. I fell in love with the guitar because of the instrument and acoustic and electric are two different instruments. Look at the style of music your into and pick one.
It is true that acoustic will build finger strength and such quicker but it won't make a you a better player. I know plenty of acoustic only players who can't do anything with an electric at all. They just don't know how to play it. It works the opposite too obviously.
I would say learn on what is going to inspire you to play. And then later if you want to expand to the other than thats what you should do, my friend is giving me her acoustic in a week or so cause she never uses it. I've been playing a few years and think I am a pretty decent guitarist (electric) but I am pretty crappy when it comes to acoustic mostly just because I play on a electric, usually in drop d or Eb standard and use .10 gauge strings with pretty low action. Acoustic is almost the opposite of that. But my guitar is perfect for the kind of music I am into so it works out.
Like I said pick whatever is going to inspire you to play because thats the important part. That you want to play and it is never a chore, it won't matter what instrument you start on if you don't like playing it.