Every artist has their own specialty - some artists are best at portraits, some dominate in old school style, some are known for their macabre masterpieces and others are best at Celtic designs. Then it also comes down to finding an artist that you personally click with - someone you feel comfortable with, someone who translates your vision properly, and someone that you can see yourself spending a few hours or more with while getting your tattoo.
I can't tell someone who would be the best artist for them. I have my own personal favorites, but that doesn't necessarily mean they are the best artist for someone else. Take the time to interview potential artists and find out what their specialties are. Make sure you know what you want and find the artist you feel best suits your needs. Be willing to pay for quality, be willing to travel if necessary, and don't be afraid to walk away at any point from someone you don't feel 100% comfortable with.