I personally dont prefer yahoo.due to some reasons the search engine of my pc was changed to yahoo as default for a few days.
And I really faced a tough time during that.the yahoo search engine is worthless.it doesnt have even the simple information in it.
Whenever I wanted to search anything the information available was very much limited or sometimes even I couldnt get the information. Every time I had to change to gmail for getting all the required information.i would definitely say that the yahoo search engine is useless.