I think any person who responds to your inquiry will have a subjective opinion regarding the answer or answers.Some of the people that reply will say that a large web host has 10,000+ customers, whereas a tiny one has less than 10,000.Likewise for staff members or servers.
As an alternative, you may consider the company's worth; if it is a publicly traded company, you can determine its size by looking at its market capitalization.In my opinion, there is no clear cut difference between large and small web hosting providers.
According to my estimation, small businesses have between 0 and 500 clients, medium-sized businesses have between 501 and 1000 clients, and large businesses have 1001 or more clients. Companies that host websites come and go.
Due to the fierce rivalry, web hosting firms come and go on a regular basis. Furthermore, a sizable portion of businesses aren't legitimate businesses and aren't registered to conduct business. That is an additional consideration.