If you are eligable for business 250 on C & S pricing is competitive, plus you have the option of express with C & S.

Not the same satchels. 

Processing is different. Ebay you do one at a time and its added to ebay invoice, C & S you do a batch and pay via a checkout process using CC or paypal, few more steps but you are batch processing. With Ebay print oine label on one sheet C & S upto 4 labels per sheet

For ebay labels I set print preference to two pages per sheet, use one size for invoice, the other for label. i dont seperate until I pack each order that avoids accidently putting wrong label on wrong order, something I often did with C & S no matter how careful I tried to be.