Buy and save all of them! that's my motto.
nah really thou doesn't matter which you buy it's never gonna stop the endless abuse Betta's receive.
I will say one thing tho, betta pellets is one food I WILL NEVER ever feed any of my Betta's ever again!!, It's not all it's cracked up to be!
I blend and mix my own fish food,
When I receive any "rescue betta's I'm often given betta pellets, Which I use to trash first thing!,
But that's wasteful so now I slowly delve them out to my Goldfish...
good luck on your choice