Once you're in medicine for any length of time it quickly becomes evident that there are a variety of opinions on any given topic. One joke is that if you ask 10 vets their opinion on something you'll get at least 11 answers. Why does this happen? Part of it has to do with differences among experts, which articles someone reads, which lectures they attend, how they were trained in school, and so on. But I believe that a lot of it has to do with their personal experiences.
Like it or not, everyone is influenced by what they have personally seen and done. These cases and events will guide future opinions and decisions, and will sometimes result in disagreements among professionals. For example, let's take the recent discussion on GDV ("bloat") in dogs. I see around 100 or so pets every week (more in busy seasons), so I have around 5000 patient visits every year (yes, some of these are repeat visits). In the last 10 years I have seen 2 cases of bloat. Someone who works in emergency medicine may see that many cases in a month. So my viewpoint is going to lean towards the infrequent nature of the disorder, while an emergency vet's opinion will skew in the opposite direction.
One of the things new graduates have to get used to is that the strange, weird cases they see in school don't happen often in general practice. Veterinary schools normally run as specialty referral facilities, so the cases seen by students are not representative of the cases most of them will see once they graduate. Common, straightforward cases never make it to a referral practice, so those students have a skewed set of cases to learn from. When they graduate and begin working, they have to somewhat re-learn the simple, daily things that they will actually see regularly. This can be a bit of a mental transition, as their minds gravitate towards the cases that they personally saw, and the cases in private practice aren't normally that odd or difficult.
The skills of a vet are also directly related to their personal experiences. Many years after graduating I learned that one of my former anatomy professors was doing some relief work for a practice that I occasionally worked with. We sat down and talked one day and I discovered that she had never been in practice before. She had gone from being a vet student to an internship to faculty. Then she proceeded to ask me questions about exotic pet medicine. Now that was a real shocker! One of my old professors was asking ME questions! Though she was an anatomy expert and had authored a text book on feline anatomy, she had never really dealt with exotics. And even though I'm not an exotics expert, my interest and experience outweighed hers. Because of different experiences, I was teaching one of my teachers!
These are some of the reasons why you will get different opinions from one vet to another. It doesn't necessarily mean that one is more right than another, as studies and hard data have to be merged with what I call the "art of medicine". This is when you have the unquantifiable knowledge and feelings that go beyond the pure science. It's still a valid influence on medical decisions, but is where you can get differences between doctors.