Which Android Phone To Buy?

[Jake]

Hey, so the situation is that I will be on 3 Network and the only really good, cheap android phones on there is the S4 Mini or the XPeria M.

I have not idea which one to get as the screens are 4 to 4.3 inches which isnt that big but im only 13 so i dont need a big screen so the screen sizes on both are great.

But I want to know these things:
Which will actually last me 2 years? I'm on a 2 year contract.
Do they both get all the Android updates?
Which has a better build quality?
Which is best for mainly texting and apps like Facebook, YouTube, Snapchat and Internet browsing?
And which is just overall better?

A lot to ask but I need to make a good choice.

10 points awarded to vbest answer!

Thanks guys x