More than a Mouthpiece
One of the reasons bits are my favorite piece of tack to learn about is they combine the science and the art of the equestrian sport. In the laws of physics there is always equal and opposite reactions, are consistent formulas of how forces are applied. This can be broken down to bits, explaining how the pressure of the rider's hands will affect the horse's mouth. The other side is the feel, the art and the dance of riding horse's and the skill of the rider to play the instrument of the bit.
When evaluating on how a bit will work in a horse's mouth it is important to look at how the whole bit will function as a whole and not just a singular part. When comparing these two bits, they both have a very similar mouthpiece but due to the shanks and the mechanics, they will have very different reactions for the horse.
The first bit is a lovely Sweetwater curb bit. A Sweetwater is used to describe a low very wide port that allows for tongue relief and sit on the bars of the horse's mouth. This is a very mild mouthpiece. However, due to being a shanked bit there will still be an increased pressure compared to a snaffle. *tune in for a future Tack Tip Tuesday about learning the pressure ratio on curb bits*
The second bit has a very similar mouthpiece, but due to the tall purchase, long shanks, and especially the metal attached curb strap this bit will activate quickly in the horse's mouth and apply a large amount of pressure quickly.