There is a plethora of information on the WEB about Water vs. Oil. Yes, there is a difference in brands, and in order to understand that difference, you have to know what the different ingredients do.
For example, in oil-based urethane, there are 'solids' that help stabilize the urethane. The amount of solids can affect the quality of the finish, among other ingredients. Here are just a few articles that talk about floor finishes. If you search for keywords like oil and water in the enclosed articles, you may get 'taken' right to the guts of your question.
The more you read, the more you can make an informed decision. And once you understand the major differences, you'll understand why one Contractor chooses a particular brand (and type) vs. another Contractor. In short, 'they' have their reasons. Once you've enlightened yourself, and have more ?'s, you know where to find us.