There is "magic" to 18 holes because like it or not, it's become the de facto definition of a "round" of golf whether ball or disc golf. It's the unit of record for the way many official stats are kept. The hole scores in sudden death are not retained or added to the 18-hole scores for example. When rounds are different from 18 in DG, the stats are adjusted to an 18-hole equivalent whether you're talking scoring averages, handicaps or ratings. Playing 9 holes either feels like practice or just half a round. That's why I believe 9 hole layouts designed with dual tees numbered from 1 thru 18 has become a more satisfying way to play a course with just 9 baskets - you're playing a regular round. When you play 24 or 27, while it's bonus disc golf, I can't get away from feeling like I'm in an overtime game, overtime is still official but not really the same as a "regulation" round. It's also tougher to have a really hot round on 27 versus 18 holes because with more holes your overall performance has a natural tendency to move toward your average skill level.