I liked both but have a preference for Seven, especially in season 4. I do wish that they hadn't humanised her so much. I'd rather she'd been used to explore the Borg and what they might have become without the assimilate everything aspect. It might have been used as a long term arc in relation to the Queen's statement of allowing Seven to remain on Voyager. Instead of the Queen being standard villain #1424355, she and Seven could have been a longer arc about getting the Borg to change from the monsters they were.