Yelp is built for the crowd: many reviews, many photos, a rating that averages everyone who walked in. Femente is built for the opposite question, which is where the critics eat. If you want a critic-vetted table rather than the most-reviewed one, that is the difference between them.
Yelp covers almost every business, with photos, hours, and a wide base of user reviews. For a casual local question, “is this place busy, cheap, and decent right now,” it answers well.
The rating is a crowd average, so the places that rise are the ones a lot of people visit and rate.
Femente does not average the crowd. It ranks restaurants on professional critic ratings, reading Michelin, Gault&Millau and other guides, and maps the results across 65,000 restaurants in 1,200 wine regions.
The tables that surface are the ones critics rate, not the ones with the most reviews. That is a narrower list, and for a special dinner it is usually the more useful one.
A high Yelp score rewards popularity and consistency. A Michelin star or a critic's pick rewards the kitchen. Both are real signals, but they answer different questions.
For a quick bite near the office, the crowd is a fine guide. For the dinner you booked weeks ahead, you want the people who eat for a living.
Femente maps restaurants next to the wineries in each wine region, so a day of tasting has the right lunch built into it. If you are planning a trip through Napa, Tuscany or the Loire, the food is part of the same map.
Yelp is organised around a business and a city, not a wine region and a route.
Both, for different nights. Use Yelp for the casual, local, is-it-open question. Use Femente when the meal matters and you want a critic-vetted table.
If you had to keep one for fine dining and wine travel, keep the one built around critics and the map.