Fireline is fused strands of spectra and dacron. It's not spun spectra like other lines. It has far superior abrasion resistence, great for fishing rocky areas. It's flatter then most lines and takes some time to break in the coating and soften it up.
I've used PP ,Stren and a host of others ,the best for abrasion by far is Western Filaments XP ! Check out Sport Fishing Mags braid comparsion chart from last yera ,WEstern head & sholuders above the rest on all fronts! Their HC is by far the on eof the easiest to slpice and probably stronger than many competitors,however can't be beat for the price !!
No mystery breaks like PP it's cold fused to prevent weak spots ,diameters same as any qualtiy braid on the market ! Ice switched to it exclusively and for the past two seasons no problems period!!
my experience: first superline ever was powerpro last summer. Within 1/2 hour i was absolutely hooked because it broke in and was just limp and very castable (I hated mono and the coils on my spinning gear).
then i read a bunch of recommendations to try fireline crystal, how it blew PP out of the water, how smooth and limp and etc etc etc).
I spooled it up andi regret it for the largest reason:
It coils on my spinning gear. The 20lb spool i bought in white just plain has a wicked memory, and i've been hoping everytime i go out that this will be the day is breaks in, and it has yet to do so. Granted the stuff has yet to break on me, but to me its not fishable.
So in short from my experience:
spectra (PP) = limp, no memory, light coating that breaks in fast
fireline = thicker wax like coating which seems to promote line memory.