I have sold both brands for years and have used both an equal amount of time.
The Spieglers are way ahead of every brand I have tested when it comes to quality. Their fittings swivel for a perfect fit although I rarely have to alter the original orientation from the way they come right out of the box. All Spiegler lines are DOT approved and most importantly their fittings don't corrode (Galfers are terrible for this) nor does the anodizing fade out like every other brand I have used.
As far as performance goes I defy anyone here to tell me they can feel a difference between one brand of braided lines lines versus another. I can't and I get paid to find differences like that... The only time I have ever felt a difference is when I switched from a -3 line to a -2 etc, but with all things being apples to apples they all deliver the same performance. Which is why I tout the build quality as the selling point as I want to buy the lines that are going to hold up the best and still look new years from now.