Best 1/36 King Tiger "Henschel turret" out there?

What, in your definition, constitutes "the best"? Almost any one of Dragon's latest offerings will build up impressively, and Tamiya's older Henschel is still a fabulous kit. The offer a separate box of  indy link tracks for it, and it is an easy-to-build and nicely detailed kit. They even have a nice and more-recent "Ardennes front" one which is a later, no-zimm model.

And any kit you choose can always be dressed up with any number of PE kits out there. You can turn just about any of the most recent kits into a showstopper.

From my research, I'd opt for the Dragon Battle of the Bulge kit. It has everything you need that you won't be able to get in the Tamiya kits: engine screens, magic tracks, aluminum barrel, wire cables. You can get them off of ebay, though the bidding can get competitive.

what tigerman said!  Unless you want to spend a bundle on AM stuff, in which case any your aforementioned kits would work.  The new Academy kit does build into an interesting "Last Production" version which, I believe,  no other kit does out of box.

You get some bonus paratroops as well. They'd look good riding on the rear of the beast.

Dragon makes a 'Final Production' King Tiger which includes the Transport Tracks its kit #6209

I like the Dragon Kits better.  The Battle of the Bulge King Tiger is an excellent kit and you get the brass shells, PE parts and 5 figures at approx the same price as the Tamiya kit.  I almost exclusively build Dragon Kits because you get more value for your $$.  So if you want an early model King Tiger then thats what  you want. 

 I also have the Dragon Porshe KT w/ Zimm and its also too an excellent it.  No fit problems, no flash, PE metal detail parts, alum gun barrel, metal tow cables, you can't ask for more.