Shipping "basics" question....

Am I missing something?

My site is set up, and now I am down to setting up the shipping modules. I set up "UPS" and it does successfully calculate the UPS shipping rates in the "cart" (and adds it in the invoice). I see that Opencart also comes with a Fedex module, BUT.... I see that a lot of people are "purchasing" Fedex shipping modules for Opencart.

I guess my question is "why would one purchase a Fedex module when one comes with OC?" Doesn't the module that came with Opencart work as well as the UPS module? I appreciate your input.

I believe the built-in one had a few bugs, last time I heard, so Qphoria's extension is a popular one if you need Fedex shipping rates. Feel free to try the built-in one first, though, to see whether it will work for you.