Staintunes are stainless steel, and will yellow with enough heat, but it can be polished out. Thunderbikes are chromed and won't discolour, but they can rust if scratched etc. Staintunes are a bit more expensive, and have a more high-pitched note. There were some bad Thunderpipes are year or two ago that had poor chrome and rusted but these were replaced by Thunderbike without question, and since then have shown no problem. Both have removable baffles if you really want to shake windows as you pass. If staying with local manufacturers concerns you, Staintunes are Aussie made, Thunderpipes are kiwi.
I had a T100 loan bike with Staintunes (which apparently sound the same as the America/Speedy ones) while my bike was being serviced and liked them well enough, but I preferred the sound of the Thunderpipes and ended up with them.
