Hi Father,
I'm no expert but I think...
The first shoe - the HJ Flow - is for jumpers who have a faster run up, approach the bar slightly more straight on and take off further away from the bar - and have a longer, floatier jump arc?
The 2nd shoe - the HJ FL (also known as the HJ Stability) - is for jumpers who approach the bar very much side on and take off closer to the bar with more of a straight up and down technique.
The Adidas athlete Blanka Vlasic uses the HJ Stability but if you're not sure, the HJ Flow is the more versatile of the two and probably the one you should go for.