Try for the artist name always. That way, you know if you have misspelled a file name or something. If in case you type 'TAIYÔ NO SIHTA' instead of 'TAIYÔ NO SHITA ' , then you will get almost 0 results.
Go for the artist name. That way, you can come to know of some of their other songs as well. Plus you can find your own. Popular artists always have plenty of songs. Hence it is not a problem to find their songs directly. But if the artist is relatively new or not so popular, then it's always better to go for the artist name rather than the song name.