I wouldn't trust the information that was given to you at all. IMO, it sounds like the person who gave you that info has very little experience with trial dogs, and is just spreading the myth, that many people who don't know much about HB dogs, have a tendency to spread.
I happen to own a Horseback Brittany that runs All Age trials throughout the US with a Pro trainer. She finished in the top 10 of the All Age dogs in the country last year on the Brittany circuit at only 3 1/2 years old. She is currently in the top 10 again and she still doesn't turn 4 until June. She competes at the top level against the best brittanys in the country. She is a big running dog off horseback, but she is a very nice foot hunting dog when I have my shotgun in my hand. Trial dogs are typically the best of the best when it comes to range, nose, bidability, and such. Those same atributes are exactly what you want in a hunting dog. With regard to range, you can always bring a dog in, but it is much, much tougher to push a dog out. My brittany easily makes 500+ yard casts when running off horse, but she is typically a 50-200 yard dog when hunting off foot. She will run closer when the cover is thick, and range farther in the praries of South Dakota. There is no guarantees of anything when chosing a dog. No matter what anyone says, its a crapshoot. The only way to improve your chances of getting a great dog, is to try and get a dog from lines that have proven themselves in either competition, or hunt tests. The next best thing would be to get a pup from hunting dogs that you have hunted over and can verify their ability. If I were in your shoes, I would look for a dog from the best trial lines you can find, and afford. Titled trial dogs have proven they have the physical ability, the mental ability, the nose, and the training ability to compete against other dogs and win. I would ask the person who told you that trial dogs aren't any good for what your looking for how much experience he has with trial dogs. When we got our dog, I asked the trainer I now use if he could hunt over his All Age trial dogs. My first priority was having a great hunting dog, if she turned out to be a trial dog, then even better. His response was, "every single one of them"!