There is a list here (vs. Google) https://opencagedata.com/guides/how-to-switch-from-google-ma...

though really the key difference is the fact that we use open data. Googles data is not open, this significatly restricts what you can do with the data.

And here is a similar comparison versus running your own Nominatim https://opencagedata.com/guides/how-to-switch-from-nominatim

Please let us know if anything is out of date or can be made more clear. Thanks.