Paybear does seem like a professional site. Their interface looks great to work with as well.

They are indeed relatively new. I have no idea how much you can trust them with at this stage. Haven't seen any negative reviews around though.

Coinpayments and Shapeshift are two of the largest and most trusted payment gateways. Though shapshift doesn't technically allow you to store funds with them, but only serves as a altcoin -> bitcoin converter. Coinpayments has a lot more flexibility and there's a range of things that you can do with them, including storing funds in their wallets. Bitpay on the other hand is more working with fiat type of site.

Up to you, do some research on your own part. But these are the main ones.