I don't agree with you. There's a real, undiscutable difference between the visual of the OAV and TV serie. As a big fan of Kakinouchi's work, I was very disapointed not to find her "touch" on the TV serie. You certainly know that she didn't work on it.
The effort given to the OAV is impressive. Even know, it is very difficult to find such a remarquable graphic work. That's the reason why I practicly never buy cels from TV.