Mechanics are a little sketchy to use as an argument, as they were different in Morrowind as well. I'm basing my argument on the fact that within the lore of TES, the Vampire clans are vastly difference in habit, appearance and lifestyle.
The way I see it, the mechanics are meant to represent the habits of the clan, and are simply done so in an imperfect fashion. Kind of how numbers are used to represent measurement, but are an imperfect system (see: Zeno's Paradoxes). Therefore, by examining how similar they are between games, I think it's a valid comparison.
There is usually a good reason that entities adopt the traits they do, and if they all had the same necessities then it's kind of logical that they would all have similar habits and traits, which isn't the case.
But they're so similar as to be almost exact. The only major mechanical difference between vanilla vampirism in Skyrim and Oblivion is how the sunlight damages them, which can be chalked up to a number of things, including changes Bethesda made based on user feedback.