I think Taurus isn't that great of a company and I don't like ruger (but my uncle loves). So I'm of no help in that category. But maybe I can persuade you on the ammunition sizes.
If you want a .40, your right about the ammo being a little cheaper. Plus it will be easier to shoot. It's a great round and the whole reason why it was invented was to have the advantages of both 9mm and .45 put together. Most all police departments have this as their standard issue round.
But honestly I wouldn't even bother with a .380. That's a chicks round (no offense
). I would go with a 9mm if you want one of the smaller sizes. It takes all the benefits of it's "little brother" and then injects itself with steroids. lol
9 is super easy to shoot (most of the time), pretty cheap, and would work very well as a self defense handgun if need be. You can get 500 rounds of good metal in 9 mill for $100 and that's in Cali! .380 is the step up for kids from a .22, don't even waste your time.
Remember this though when you finally decide on a piece to pack heat: when it comes to guns, most of the time
, you get what you pay for.