Without even watching, KOOKS !
USA made.
Single piece multi-axial primary’s.
Primary layout follows firing order at collector for rotational pulse scavenging.
Collector spike.
Primary’s properly air-gapped to mitigate false knock.
Not 100% sure but I’d wager domestically sourced 304 grade stainless steel.
I think GregO above outlined some of the differences that largely go overlooked.
Build quality and fitment are easier to observe. Material quality and dimensions, weld locations and conformance, etc.
What you can't see is the actual "design" of the headers. It's why some headers give off a different exhaust note than others.
There are subtleties that you might not see in how the designer put together the overall plan given the space restrictions. While the power differences may not be large at OE levels, but even a 5 hp difference when extended out into blown power levels can be substantial.
Lastly, with such a large purchase, the "buy once cry once" factor comes in. Once you sink the money and time into swapping headers, it's difficult to go back and upgrade.
You'll get 90% of the performance out of the budget header options, but it's truly one of those mods where spending the extra 15-20% more on the top products is worth the additional squeeze.
According to my shop, the TSP headers are easier to install. They do a few sets of each every week. And the TSPs are the better to install. I have them and they work well.