Making Money with Android

Google Ads - google services or lib?

Hey everybody,
Can anyone point out pros and cons of choosing either of the approaches implementing Google Ads [1][2]? What’s the difference (beside the obvious like implementation etc)?
Cheers

[1] https://developers.google.com/mobile-ads-sdk/docs/admob/fundamentals#play
[2] https://developers.google.com/mobile-ads-sdk/docs/admob/fundamentals#android