Xapo and coinbase are not actually a bitcoin wallet, they are centralized payment processor .
I at all cost try to avoid them They don't share private keys with you and can lock down your account anytime they want.
Have you used any bitcoin online wallets. If you used it before your answer will not this you have answered here. Coinbase and xapo are most of the preferred wallets around forum. miliions of users using coinbase wallet for long time. Keep investing on the bitcoin and buying and holding also can be done by the coinbase trading site. You are this wallet is good means what would be perfect wallet and what wallet you are using?
For private key they will give the information in their FAQs itself.