None are particularly hardier than any of the others, remembering that they are all the same species of fish, it's just that they have been bred such that their tails and finnage are developed in certain ways.
It's like asking which breed of dog is hardier - red setter or king charles spaniel or dobermann - they are all the same species, but bred to have different features.
Those prices seem exceptionally low, though, I would have to be asking myself why this is, is the LFS not making enough profit, are they weak stock that the LFS or the breeder wants to get shot of, are they older fish, and that's why the breeder wants to sell them cheap.
Also, do you have the right tank for a betta, is it cycled, etc.?