Hi, I tried a bitless bridle on my mare (bit of a head shaker). Tried the Dr. Cook after reading all the bumf about them, they are supposed to 'cure' head shaking. Unfortunately, didn't cure my mare, made her much worse, she really hated the 'head hugging' sensation of it. Suppose it depends on what reason you want to try one. My old cob is great in his. Suppose it is trial and error, what suits one doesn't always suit another. Good luck.
I ride my geldings in Dr Cooks. As poodle20 says, they definitely don't suit all horses (in my own personal exerience it has always been headshaking mares who don't like them - not a sweeping generalisation by the way, I have actually known two headshaking mares who didn't like them at all, but I don't know any other headshaking horses! Maybe it's a poll pressure thing for them?)
You can have one on a 30 day trial from the company who supply Dr Cooks in the UK, which should give you time to see if your horse likes it. I must say I buy mine from the USA as it is cheaper for me.
I wouldn't dare ride in a hackamore because I don't like the idea of levering on a horses nose (I'm not always the lightest handed of riders). Also, if I was going to get a side pull I might as well ride in a headcollar.
I used a Dr Cook's on my TB - he went much better in it and was much more relaxed (he was quirky to say the least) - rode him in it for 2 years and sold him with it. Never had problems with brakes or steering. They are definitely worth a try.
I rode my Welsh D in a Dr Cook bridle and he went much better in that - he didn't lean on it in the same way he leant on any other bit. I also had much better brakes and steering with it and also much better for when my novice daughters rode hime.
I also tried a Dr. Cook - did not like it. As other options are limited I made my own.
It was almost impossible to get anything over my horse's ears at first and anything that 'jingled' was a definite 'no'. I had to design something that could be put on easily and made no noise.
After a lot of patience and rebuilding of trust, we have just 'moved on' to a more typical looking bridle - but still bitless. If you can't find something suitable, let me know!