Many people say that the first thing a beginner should do is finding the most comfortable pitches he/she can sing and then sing there. I myself, a beginner, don't know if "most comfortable pitches" really do exist. Sometimes I sing a little higher and sometimes a little lower. As a high tenor I probably project best with the higher pitches but it doesn't mean that the lower pitches is always less comfortable. The same thing applies to my speaking voice. I have a higher speaking voice but I am not sure there are specific pitches that are the "comfortable pitches". Different pitches have different sounds eg higher pitches have more power and projection but lower pitches sometimes require less power to sing but are not always easier for me. It's the same thing with piano. There are 12 different keys in which you can play a melody but no key is the "most comfortable". They just feel different.
Are there really pitches that are the most comfortable for a singer and for a speaker?