Test, test, test
Test a One-Page Checkout especially if your average order value is low and you’re selling impulse purchases. If you can, split test against a multi-step checkout, because it is not clear which option will yield higher results for your specific industry and store, as evidenced below.
One-page checkouts and digital wallets (Amazon Pay, Apple Pay, PayPal One Touch) have improved mobile conversion by up to 10% at launch. For Power Support, they say a 26% increase in orders within two weeks after installing Amazon Pay. (source)
For GetElastic, single-page checkout outperformed its old multi-page checkout by 21.8%. (source)
This type of checkout can more easily help you identify bottlenecks. It is also typically less cluttered and overwhelming to look at as it minimizes the amount of information displayed and required at any point.
Same conversion rate?
This article shows that both one-step checkout and multi-step checkouts convert about the same, with perhaps a very slightly higher conversion rate with multi-step checkouts. See the graph attached below.