As always with these comparisons the origin of the data is key. This is based on data from SimilarWeb which states these sources:
1) Global Panel: A global panel of opt-in panelist who agreed to share with us their digital footprint
2) Direct Measurement: Websites and Mobile Apps owners who share data with SimilarWeb directly
3) Partnerships: Data from partners with millions of subscribers
4) Public Data Sources: Proprietary technology and indexing engines that scan hourly for every existing public data point