I have the Spruell's. I do not know if they are better than the others. I got them because, I think, they are the only ones that have each tube equal length. Also - they look cool. (but not as cool looking as the Shankle ones.)
My engine is very strong and has a lot of mods that all finally came together well for an incredible street set up- not sure how much power to attribute to the headers but at least they look badass...
Current: 69 GTV, 2019 Stelvio, 95 Porsche 968 cab
Past 74 GTV, 69 GTV, 74 Spider