Hi J,
It depends on the numbers of total pieces if you are looking for upto couple of hundred customized pieces then it may worth taking into consideration else for common purpose most of the screen printers in your local area may produce satisfactory results."if it is a basic range of tees"
in manufacturing cost cutting & quality customization may only be possible if incase you are making few hundreds of pieces roughly 50 pieces x 5 styles or any numbers closed to it.
using custom manufacturing for any quantity below 250 usually increase the cost by 10-20% of the normal "wholesale blank+ custom screen printing" pair's value.
hope it will help you understanding the better choice.