Depends on what you've got to heat the blade with. An oven with control temperatures and a good quench tank, either method is just fine. A forge, more dicey for 52100. If heating with a torch then an edge quench would be best since it will be VERY hard to control the temperature.
I use a lot of 52100 for my chefs knives, and I always harden the entire blade. I draw back the spine between my two temper cycles. If you do an edge quench, and the blade is bent when it is being used, it will stay bent, this way it can spring back from a little bending.