Ally - there's an old saying in the script writing business: there's nothing as important as the first 10 minutes of a movie - except for the last 10 minutes of the movie!
I think it applies to golf courses as well, at least for me. During the middle portion of a round, I simply take what comes, as it comes: hard, easy, short, long, 3s, 4s, and 5s, and if the golf holes are good I don't give it a second thought.
But I do like something particularly good and/or interesting in the first 2 or 3 holes, as that sets the tone and to a certain extent my mood. And then near the end, it is gratifying to be snapped out of whatever lull I may have fallen into by a couple more particularly good golf holes.
And I find that it doesn't matter to me much if those are difficult holes or easy ones - I've enjoyed (or not) both types of finishers.
So I'd say: end the course with the best 3 hole stretch you have, and start the course with the 2nd best 3 hole stretch you have.
Peter