Hi bigkilla

I have both of the tanks you are thinking about and............

I think the Pershing sounds the best of all the Tamiya Tanks, it clanks away while you run it, and the faster you run the faster the clankin!! It also has lights, and a rev function when you first start it up. Its a pretty straight forward build and you dont really need any extras for it. Just try to keep all youre cables nice and tidy, there isnt much room in there.
The King Tiger took a LOT of tinkering to get it working properly. And I added a few bits and peices ie. metal track etc. (more money!!) But it does look cool....
The KT has two different start up sounds, electric and manual, but no lights or rev.
Any vids you might see dont really do the sounds of any of the Tamiya stuff justice, so try and see one in real life.

All in all I bought my Pershing first and never caused me any build or running problems. My second build was the KT and it was an expensive nightmare!! But the KT is my favorite of all my tanks.

You decide!!