Paybear and Bitpay are completely different if you want to buy Bitcoin.
Paybear only gives you their API for payment gateway, Paybear supports multiple cryptocurrency out of the box when compared to Bitpay payment gateway.
Bitpay on the other hand has many services to offer, something as simple as buying bitcoin to Bitcoin Debit Card and Payment gateway.

If you want to buy Bitcoin, you can find exchanges that has lower/higher rate than Bitpay.