Pay as you go vs contracts in the US for mobile phones


I’m wondering, for the long term, does it make sense to go with contracts for mobile phones in the US?

I found a site known as “calling Taiwan” which allows you to buy US sim cards in Taiwan, so you don’t get stuck without internet or whatever the moment you land.

Is AT&T better than T Mobile? I notice T Mobile is cheaper. They have a plan that offers 1gb full speed internet (that turns into Edge once you go over) and unlimited voice/text for 50 dollars a month.