German industry first began working on heavy tank designs in 1937, even though it was believed at the time that the PzKpfw III and IV would be more than adequate for the coming battles. But when the German Panzers in Russia encountered the Soviet T-34’s and KV-1’s in 1941 it was all too apparent that a new heavy tank was needed. Ultimately, this resulted in a specification for a 45-ton tank with an 88mm gun, heavy armor, speed and manuverability. The Porsche firm began working on this new tank design but encountered serious complications. The Henschel firm then began working on its own model under the direction of Dr. Erwin Aders, drawing from its previous work on heavy tank designs. The two firms were to have prototypes ready for inspection by Hitler at Rastenburg on his birthday, April 20th, 1942. The Porsche and Henschel tanks were put through trials and, in spite of Dr. Ferdinand Porsche’s friendship with Hitler, the Henschel tank won, in large part due to its superior maneuverability.
Dr. Erwin Aders
The “father” of
the Tiger I.
The Porsche prototype Tiger. The familiar shape as designed by Henschel.
Production was ordered to start in August 1942. It began at a rate of 25 tanks per month and peaked in April 1944 at a rate of 104 per month. It took 300,000 man hours to build one Tiger, almost twice as much time as a Panther required.
this is a cut and paste from http://www.alanhamby.com/history.html
looking at these two tanks i do like the Henschel design better.
:o 
