Which is better: T-Mobile or AT&T?

My mom and I both have T-Mobile and my Dad has AT&T. Before buying me the phone, my parents closely considered on what server I should have. They put me on my Mom's plan because it was a cheaper offer. I have a samsung galaxy S and it's a really good phone. But I'm really interested in the iPhone. Both my parents have it and all of my friends do too. A lot of people also have AT&T and very few have T-Mobile where I live. With T-Mobile, I get spotty connection and my text messages don't always go through. There are also many times where I don't get service, unlike my AT&T friends. Also my 4G doesn't always work. I know T-Mobile is a cheaper plan, but I still want AT&T. What do you guys think? All advice is helpful!

I've had at&t since my first phone and i've never run into problems with connection. I usually have more coverage than my friend with t moblie. It might depend on where you live though, mainstream areas like California might have cell towers than other less populated and wooded states.

Ok. I'll list advantages for both carriers.
AT&T:
Better Coverage.
Faster Data Speeds (LTE)
More Good phones (iPhone, Lumia 920, HTC Once X+)

T-mobile:
Cheaper
Still has some good phones. (But AT&T has them all).

I say if you can afford AT&T, they're clearly better.

The T in T mobile stands for Terrible! I've had both carriers and if I had to choose, between the 2, it'd be AT&T. You should try Cricket. They have great service in lots of areas and you can still get your iPhone. Plus they have unlimited plans for about 70 dollars. I switched to Cricket from t mobile and I'll never go back! Lol

Verizon and AT&T are tied for first place, Sprint takes third, although reports have shown it's almost tied with Verizon and AT&T, t-mobile comes in at fourth, and metro pcs is fifth