FedEx vs USPS - which is preferred?

[h linamen]

For those of you who ship small packages, which is preferred FedEx or USPS? I guess primarilu I'm wondering which is less expensive. I sold an item on eBay and shipped USPS in a box about 10 x 8 x 8 less than 3 lbs and was shocked to pay $12.75 for one week delivery and would have been almost $16 priority mail. That's about double what I used to pay a couple of years ago. Getting ready to ship another smaller package and don't want to pay excessively.