Freeze dried bloodworms aren't actually a healthy source of food because it lacks many essential nutrients. Pellets are usually better because they're made to be a balanced diet for them.
Actually anything 'freeze-dried' or dry for the matter is bad and often leads to digestion problems that lead to a lot of medical issues. It's mostly because of the low moisture content, so even dry pellets are bad in that department. What happens is that they will often expand when they absorb water in the betta fish's stomach and become up to 2-3 times their size. Your betta fish's stomach is roughly the same size of their eye, so feeding them too many pellets can lead to things like bloating, constipation and or SBD.
If possible, pre-soak your pellets in water before feeding it to them. And usually only 2-3 pellets twice a day is good enough.
And if you can avoid it, don't feed them flakes because it's hard to measure a healthy amount that should be fed to them.