Descartes XPS Ship

Probably the best shipping app on Shopify, I've tried about 4, including this app. I was looking for better shipping rates and this app offers the best service by far.

Integration
Shopify, Amazon, eBay, Etsy, Opencart, OSCommerce, Prestashop, Magento, PayPal, Volusion, BigCommerce and a few more. So you can import all your orders automatically from several different channels

Goshippo integrates with ebay and shopify, but I did not check others
Netparcel only integrates with Shopify
Shipping Easy I didn't check for integration with other platforms

Fees
XPS - no monthly or additonal fees - to pay you need to add funds
Shippo - no monthly fees, label cost plus 5c
Netparcel - no monthly fees - bills your card manual or automatically
Shipping Easy - free if you post less than 50 per month, thereafter sliding scale monthly fees

Rates - USPS
Best rates I have found for USPS, cheaper than Shippo, Shipping Easy and, if I'm not mistaken, Shopify. Note I mainly use flat rate boxes

Rates - Couriers - FedEx, UPS
If you have a FedEx or UPS account, like we have, you can compare to XPS, XPS got us much better rates, on some packages we save up to $9! NOTE - You might find that you may get better discounts with your existing accounts depending on the discounts you have.

Although XPS are not the cheapest, Netparcel was cheaper, but by small margins $1 - $3 plus/minus. I did mention this to XPS and they said they will work on cheaper. However, if you add additional insurance then you find that rates are the same or differ by a few cents, either way. XPS does have a much better UI and they will get you rates with USPS and UPS.

Netparcel only does FedEx.

Unfortunately, Goshippo will only integrate with your existing accounts, they won't be able to get you cheaper than what you already pay.

I think Shipping Easy also integrates with your exisiting FedEx account, but to get a cheaper rate we needed to contact my FedEx account rep to see if our discounts are more or less than Shipping Easy, he was supposed to get back to us and we didn't follow up, too much headache.

User Interface
I think better than all. You add sender, receiver, package type, dimensions, weights and select courier service type all on same page, and get the quote in real time, no moving between 2-3 pages. You get competing rates from 3 service providers, USPS, FedEx and UPS (Goshippo does do this but you have to go through a couple of pages and they won't be cheaper)

Live customer service, just call the number to speak to someone.

You can also handle claims on XPS but I have not tried this feature yet.

I will edit this review if needed

My main reason for using an app was to get a shipping manifest for USPS since Shopify does not provide a manifest. I tried another app and gave up after 2-1/2 hours of chat with someone who was obviously going around to various chats with other people at the same time. I was referred to XPS so I signed up, and was set up and trained within a half hour by Brendan. The next morning I called customer service. They answered the phone immediately and did my first three orders with me on the phone until I was comfortable. Easy peasy. I HIGHLY recommend XPS for ease of use and for their customer service.
GONE COUNTRY HATS