All my horses go better in a Herm Sprenger bit. My TB decided he liked it so much that he wouldn't ride in my other bridle with a plain snaffle and I had to get a second one!
They are actually different from many of the knock-offs, too. The cheaper versions are wider, heavier, and flatter and my horses did not go well in them. If you want to try a basic one, though, Horse & More bits from Dover are made under license from Herm Sprenger, so are the same design, but only cost about $40. I have one of those and a real Herm Sprenger and they are hard to tell apart, and my horses like them equally. There are also lots of places that will rent the bit to you to try out.
Tug on anything at all and you'll find it connected to everything else in the universe.~John Muir