Yes, they're all made out of the same thing (spectra fiber)... but! they're not all manufactured the same!
Some a braided round (PP) and some are braided flat (stren gorilla braid comes to mind) and some aren't even braided at all (spiderwire fusion)
Some are coated (PP and fireline) and some aren't (the older Spiderwire). The coating makes the line stiffer IMO, and some of the coatings come off too easily (fireline).
It all boils down to personal preference and trial and error. I personally like the Spiderwire and PP brand braids.
I don't care for Fireline, stren gorilla braid, and spiderwire fusion... but that's just me!
All of them that I've used will fade with use and being exposed to sunlight over a period of time.
Just because someone says they like and have had good results with a product, doesn't mean you will.