Many, many, many moons ago when Betta came in blue or red only, they were hardy little fish, absolutely unpredictable in behaviour due to their natural genetics but the fish themselves were in proportion regarding tails and fins. My dad's Betta lived happy and healthy for 7 years without illness or disease back when you had just two colour choices.
Today they are the living version of a designer handbag. A multitude of shapes, sizes, colours....frankly mindblowing what has happened to this humble little fish.
They are - in my own and others I know - experience very fragile compared to decades ago. They seem less capable of fighting off the most basic of illness, prone to diseases that the original fish never had any issues with recovering from. They still have the Jeckyll & Hyde temperment, no matter how docile it might appear, they all have a rabid tiger inside them waiting to come out and attack anything that moves.
Personally the recent Glo-Betta along with many of the other colourways and tail/fin growth types are sickening to see. To sit and watch such a tiny little body dragging tails and fins 2 or 3 times larger than they are is extremely cruel.....think of it as diving into the deep end of a pool wearing a massive wedding dress with a very long train attached.....
Betta's have a very unique body language that all owners should learn to interpret, especially when the fish have tankmates, they are intelligent fish and they do communicate when unhappy, unwell or feel unsafe or are going to attack. They are not called Siamese Fighters for no reason. I have seen these fish fight when visiting Thailand and Cambodia, it is no exaggeration to say just how capable they are to rip another to pieces and kill it....just as they will any fish like Guppies who have long flowing tails/fins...they do not differentiate that its a Guppy, they see flowing tails and fins and immediately think...male Betta on my territory...must chase away or kill. That is how they are wired, you will never ever stop that behaviour.
I have owned the more recent variants but never again. Whilst there is a marketplace for these fish, the breeders will find new ways to ruin them in the name of money and I will not be a part of that.