When I first got bettas I had betta flake food, but they didn't seem to like it all that much, once I switched to pellet they really went at it then. I guess it just depends on your fish.
I feed mine flake once in a while, but not betta flake. I have 3 different kinds of pellets, so I try to give them something different each night and fast them once a week.
i odnt know any experienced betta keepers that feed their fish flakes.
i know mine didnt like them (back a long time ago when i didnt know any better so i just bought the cheapo flakes) when i tried feeding them flakes.
flakes tend to cloud the water as well