Most natural looking front tooth crown?

The jury is out in terms of absolute crown aesthetics, but for single unit crowns for excellent aesthetics you should be looking at :
Zirconia layered with e.MaxZirconia layered with porcelainFull layered e.Maxe.Max core with porcelain layered over the top
The above list has the strongest relatively aesthetic option at the top and ends with the most aesthetic but slightly weaker (long term) at the bottom (e.Max with porcelain). 
Within this list technician and how the dentist prepares the underlying shape has a huge effect as the dentist needs to provide the technician with space to work in the mouth and the technician needs to have an overview of your mouth, preferably seeing you to take the shade. 
Good luck in your treatment - 

Kind regards
Thomas Dey, BDS, MSc

As you are concerned about esthetics, so most important part is searching good cosmetic dentist whose primary focus is on cosmetic dentistry. Now come to material, there are so many good quality materials available, but it's my advice to discuss this part with your cosmetic dentist because there are many factors that need to consider before choosing crown material eg. how many surfaces are involved, anatomy of a tooth you want, shade of the tooth, cost etc

You have great questions concerning your front teeth. Firstly, the best crown that is the most natural looking and can truly mimic your natural teeth is the Emax all porcelain crown. You should go to a dentist that will direct you to his/her lab for a custom shade with the lab technician. Do not let the dentist take a shade with a shade tab. The lab needs to see you and then custom shade it. This may take a couple tries depending on the shade of your natural teeth. Be patient and they should be able to dial it in. Also, your temporary crowns should be made as to represent the shape and size of your final crowns. This means you should be happy with the shape of the temporaries before they make the final crowns. Note that the color of the temporary crowns will not match your final crowns or your teeth. The materials simply don't match well. Don't worry about that as the custom shade will take care of that concern.Be prepared to pay a little more for this kind of service. It will be worth it.