You must try this app if you are a serious advertiser and know the value of an optimized feed. You must be willing to optimize the feed to save a good amount of money on your Google ads spend.
We have developed this app after using almost all apps from the app store. This app offers some first of its kind features not offered by any other app. The unique features are:

Point of Comparison	Google Shopping Feed App	Other Free and Paid Apps
Number of products	Unlimited, as many as your Merchant Center quota limit	Ranges from 10000 to 150000
Ability to exclude some products	Yes, based on collection and rules	You have to select products to submit to Google
All or first or specific variant submission	Yes, you can either submit all the variants or first variants or you can exclude specific variants based on rules (Coming soon)	Some apps include all the variants, one cannot change it as the first variant or exclude some variants.
Filtering and Bulk Edit	Try filtering and Bulk Edit option, you will be thrilled with its efficiency and precision.	If you have tried our "Filtering and Bulk Edit" feature, you will not like any other.
Title edit option	You can optimize the title for feed only.	You have to use the same title as you have on Shopify in most of the other apps
Description edit option	Add/edit the descriptions so that they are keyword rich and important specifications included which help in getting more relevant Impressions in the campaigns	Most of the others don't have this feature.
Promotions feed	Promotions are very important to get more CTR.	No free apps support promotions feed. Even many paid apps don't have support for promotions feed.
Pricing	Variants are absolutely free. We charge you for the products only.	Free apps don't have control over variant details getting submitted. Paid apps consider variants in pricing calculations.
Support for additional attributes	Support for additional attribute requirement like colour, size, material, pattern to optimize the feed further	No support for the additional attribute.
Support	Our support knows Google Shopping inside out and helps you fix most of the errors through documentation or Skype/Hangout call support	Free app support hardly knows anything about Google Shopping. Paid apps still can't match with the support provided by our team.

Here is a quick link to install the app: https://apps.shopify.com/google-shopping-feed

For any further query, feel free to connect with us at support@simprosys.com