Got this helpful response from USGS however it does seem that the data is available in S3 as quickly as it is in M2M API. The difference is that S3 has pick and choose for files available whereas M2M API at first only has the whole bundle available to download.
Angele Zamarron,
All raw data from the satellites is downloaded to our data stores in Sioux Falls, SD first. From there we generate the different products, and upload those to the cloud.
It might seem a little counter intuitive, but what I would recommend is subscribing to the SNS notifications but download via M2M. While the products are processed on premises first, the metadata files we maintain are updated daily. You will learn about new data faster if you are getting notifications from AWS. >However, I would recommend downloading via the M2M API as you will be able to access the data faster. We keep ~90 days of data on cache in our data stores as that is the most sought after/ downloaded data. This data