I also think Leven's the better course. And mostly for the reasons you give. The old combined course would have been superb.
I hope, by the way, that that 3 course split has 6 at Elie, two each at the others, or we may no longer be friends......
That said, my split might be 5-3-2. I like both Lundin and Leven a lot. Both have excellent coastal holes and less good inland holes. As you say, though, Leven's inland holes are better, even if Health and Safety issues would prevent them being built now.