I believe that fire blast is better solely because blast burn needs to recharge
This means that over the coarse of two turns , in reality , fire blast does 220 damage while blast burn does only 150
It is also worse if you are in a tight spot
So all-in-all fire blast is better in a tight spot
I would say for weaker Pokemon blast burn would be better and "tanky" Pokemon should have fire blast
But if you wish not to go with "slow and steady wins the race" and wish to sprint and burn energy so thst you need to recharge then blast burn is for you
NB this is mostly my opinion
Thanks for valuing it
But feel free to have your own