Solid mouthpiece bits can be an advantage and some horses take to them quite well. Others, not so much.
I attended a Dressage Symposium about 10 years ago put on with Hilda Gurney, a Bronze Medalist from the '84 Olympics, as the presenter. She said her bit wall has over 50 different items on it, and she's used as many as half a dozen in a single training session on one horse! She noted that this was probably more than what most folks will do, but indicates that even a very experienced professional has to do some "trial and error" to find what works for any given horse in any given situation.
Or, put another way, one size still doesn't fit all!!!
One line of bits I've found to be very effective with a very large number of horses is the Myler brand. These are not cheap, but are well made and come in a wide variety sizes and types. Another very well make line are the KK bits. They seem to favor the big, warmblood type of horses and can easily be too big for the mouth of a lot of light horses. But if they they fit they can work. Again, you have to look at the type and then select the size.
IMO you want to avoid anything marked with the name of a very prominant "gaited horse expert" who hawks bits, saddles, etc. I've seen some of her products and was very unimpressed (except, maybe, by their overall poor quality). Stick with folks with a good "track record."
You don't want to "obscess" over bits, but it can take some trial and error to find the ones (note the plural) that work for any given horse in multiple situations.