I never really used 'harsh' bits, but I'd only really use bits in general if they're fine with the rope halter first. Otherwise, there's no bit going in there....I also go by the words "a bit doesn't control your horse, your horse controls himself".
I've got to strongly disagree. Actually, bits were
invented for control. They do not give absolute control, but they absolutely provide more influence (control) than a rope halter does.
Bits are tools. For example, the main reason I switched Trooper over from a rope halter to a bit was that he tended to tip his nose out in turns, and a rope halter didn't give me any means to tip his nose in and teach him to turn with better balance. A rope halter gave me no control of his nose position.
Mia has always been a very spooky horse - as in 'eye-rolling, diarrhea-squirting' fearful. In a rope halter, she never learned to control her fear. In a snaffle, she never learned to control her fear. In a curb bit, I was able to keep her in one place when something scared her...and she soon figured out that the scary things ruining her life were not so scary after all.
The curb bit gave me more control. That control made it possible to train her
. If I had stuck to a rope halter, she would still be a terrified horse, winding her emotions ever upward until she mentally melted down.
Mia had no control of her emotions, and a rope halter - which we tried for 3 years - was useless for training her to control herself. A snaffle did not give enough control to teach her to control herself. A curb bit did, and using one has changed her life for the better. She is far more relaxed when hanging out in the corral today than she was 2 years ago. She isn't totally free of nerves or spooks, but her spooks now consist of "The OMG Crouch" instead of "Turn and RUN!" - and that is better for us both.
Some horses are naturally very willing and self-controlled. Others need varying degrees of help to get there. I'm currently working on transitioning Mia back to a very mild snaffle bit. I do not know if it will work. If not, she can go the rest of her life in a curb. There is nothing harsh or cruel about the design of this bit:
I will be interested to see if she has learned enough self-control and confidence to behave well in its snaffle counterpart:
Bitless bridles and bits are both tools for communication and control. Which works best depends on the horse and the need.