One of my guys wouldn't eat them, he seems to think he's above freeze-dried foods and prefers live brine shrimp, the spoiled brat.
All of my other fish love them, though not as much as frozen bloodworms. Just make sure you rehydrate them to prevent bloating. My other betta even jumps to snatch them out of my hands.
I prefer to feed the frozen ones, but when I don't have time, the freeze dried ones work well. Your guy might be spitting it out because they're too big for his mouth. You can break it in to smaller pieces, I used to do that for my guppies. Or, he might just be a finicky betta too. ;)