The KB's are popular due to price. They break easy due to bad ignition timing and/or poor state of tune along with bad ignition timing. I have used the KB-107's several times. My machinist doesn't like them much.

The Speed Pro C116hp I have used once before and currently I am using again on the currently being built engine. I also had a create engine with these pistons within. My machinist likes these pistons.

What my machinist likes and dislikes just seemed to be preference by him.

I have not seen, felt or measured any difference in performance between the two oistons. The SP116 has the coated anti friction skirt. Some around the net complained when it wears off with "I don't want that crap floating around my engine as it wears off the skirt."

I say your oil filter takes care of that and if it doesn't, you need a better filter.

The SP116 will work a little better in a iron head solely due to the slightly lower compression height that makes it easier for a lower ratio to work easier with a iron head. While it is true you can have your deck surfaced for an any thickness MLS gasket, the finer points of your build and how it gets done is your call.

I found both Pistons to be just fine. Perhaps you may want to look into there weights? Or bang for the buck cost wise. The SP116 can be found at summit being sold with rings for less than a separate purchase of each. I do not know if the KB's are available like this in cost savings or cheaper than the SP116. Perhaps one has deeper valve notchses, if you actually need it.