Today, the main difference between a lot of beginner and intermediate instruments is the trim level - basically the same instrument, but with more extras. The professional model is normally a huge step up in quality and playability, but a beginner or inexperienced player will have trouble telling the difference.
When talking about vintage instruments, the beginner, intermediate, and professional models were unique instruments, different from each other and more of a step up in playing quality the higher you went up the ladder.