Hiring a designer with a distinct style is one way to make sure the design meets your general aesthetic goals. Compared to a designer whose portfolio has some things you love and some things you hate, in various different styles.

OTOH, it is amazing that some designers just repeat the same motifs in every work they do, and make a career out of it. Another one is Michael Schwab. I love his work but it is all very samey: http://www.michaelschwab.com/portfolio_posters.html