The fins are somewhat of a personal choice, like the kind of underwear you wear.
here is how i tell my students to decide.
go mountain biking for a day. now are you the type of person who rather spin the gears in a lower gear. or are you the type who pumps it in a lower gear.
just go to a gym and watch the bikes. there are two types of people outr there.
1 - using a high gear and peddling fast
2 - using a low gear and peddling hard
both are getting the same benifit in different ways [roughly speaking]
decide which type of peddling you preffer and then buy the fins to fit your personality style
split for the fast peddler, the other style for the stronger peddler
I will say as for straps, nothing beats spring straps if you dive in an inviroment that is prone to entanglement. I just wish they made springs straps that fit the modern style fins.
nothing wrong with jet fins. except for me personaly they are to heavy, my lower body is allready very negative.
I am using an old set of Blades and find they work just fine, except for the straps, if i am going into a nasty wreck with lots of snare potential i switch to jets w/ springs and compromise