Google:
provides really relevant information;
provides instant search that saves lots of time;
connected products come with more background information;
provides avriety of file formats'
is the most popular which shows its best capabilities in general;
Bing:
has strong social integrations;
page results looks more attractive;
search history in view;
simple, easy to read, brief descriptions;
Yahoo:
This search engine mostly beats other ones because of its accessibility and adaptation to email services. When I talk about yahoo its always associated with email in my minds.