^^^ say it all
They are both hard as hell.
Blazblue = Insane amount of button pressing for giant combos
Street fighter = alot of studying to get good at a character just to get SNK out of links.
thanks for your the reply and the depress 
Don’t bother worrying about which one is harder to learn. Even if one were easier than the other, reaching high-level play would still be really hard.
Just try both and see which one you like better. In my opinion, they have distinct enough mechanics that you should like one better than the other, but not distinct enough that you can’t pick up one after playing the other.