The method of sending, ie: Content API, XML, CSV are all the same in terms of quality, or acceptence from Google.
With XML and CSV you have more features such as display ad attributes (not available in Content API)
Adding additional countries using currency conversion (not available in Content API)
My application offers the XML version, however I recommend you compare and check all the tools and apps to see which fits best in your business.
I recommend you look at both functionality, ie: can you use import rules, can you manually edit data. And pricing.
Hope this helps.
You can use ShoppingFeeder, a feed management provider. It lets you subscribe to the relevant marketing channels and connects your merchant center and add accounts within the platform. You can easily generate an XML feed for multiple channels. Check out shoppingfeeder.com/packages or start a free trial
We have developed an app Easy Google Shopping Feed App by AdNabu, which does most of the job automatically like claiming your domain and setting up your feed.
AdNabu allows you to verify & claim your website automatically. You do not need to make any manual changes to your website. We will do this for you.
In case you want to give it a try you can download it here, any feedback will be appreciated.