Hmm, how old is Mr. Beefy?
I think, if it were me (because I have been through two ACLs and two hip surgeries with my bullies), I'd be safe rather than sorry and get an x ray taken. I am some what surprised that these vets are giving you unequivocal answers regarding your dog's hips because the only way they can REALLY make a diagnosis for hip dysplasia, is through x ray. The physical exam is part of it - there are tell tale signs in gait, stance, and muscle tone - but the firm diagnosis only comes through pelvic x rays that are taken by someone experienced taking x rays to detect this condition.
If you trust your vet and you trust his experience with bullies, you can just accept the diagnosis but I would inquire as to why you are seeing a lack of muscle tone and curious gait. Sometimes bulldogs walk funny, I know Linus does and he looks like an orthopedic wreck, but he's fine.
On the other hand, if you think something is wrong, trust your instincts. You know your dog better than any vet and if you see something off or he's demonstrating weakness in the hindquarters, bunny hopping while running, fatigue in one or both hips after exercise, difficulty getting up, etc, then spend the $100 and get some x rays, if nothing else for peace of mind. Again, the benefit of detecting the problem early is staving off arthritis as long as possible and, from what it sounds like, treating Mr. Beefy with medication or supplements, if there is a problem. Once the hip is too far gone, and has become badly arthritic, your options are limited so it's probably best to find out for sure now. I will also add that hip dysplasia can manifest itself in other orthopedic problems that can be costly to fix, like torn knee ligaments.