Many people have spent a lot of time talking about challenges with Yelp reviews and their algorithm, and I don’t at all want to claim that Google will tolerate fake reviews (they won’t), but they don’t seem to have quite the stipulations that Yelp has as far as who makes the cut.
In fact, they have an even better engine for predicting “fake” reviews than Yelp. This saves small business a lot of frustration, since their customers put a lot of time and effort into writing reviews—and it is helpful for the business to keep any one they can.
It has been predicted that Google reviews will eventually overtake Yelp reviews. They are actually fairly new to the review game, only launching Google Local Search in 2012, while Yelp has been around since 2004.
Since Google has become king for online presence, it makes sense that they have enhanced their review features over the years, as well as integrated reviews from other sites (such as Groupon, Facebook, etc) into their review presentation.