I own three different version of the "Comics Are Life" T-Shirt.
As you may have noticed I went with Zazzle for my T-shirts. The answer is simple, POD, Quality & Money.
POD means print on demand. That means I don't have to buy 100 shirts and hope to sell them or I'm more sol than I am currently.
Quality. I printed the same basic shirt from Zazzle, Cafepress and CustomInk.
Zazzle was the most expensive if I remember correctly. But I got the layout I wanted, the shirt looked nice and it didn't fade after i washed it.
Custom Ink had two flaws. I couldn't do it POD style like Cafepress and Zazzle, meaning people could order them and redesign them, but I wouldn't make money off them. And I wasn't thrilled with the layout ability's either.
Cafepress. I recall a good price, but the quality wasn't there, after one wash it was very faded.
So Zazzle one, but if someone can point me to a better option that's tried the ones I have already, I'm listening.