If your looking at which is more profitable. It depends on your idea of profit.
In a Hub and spoke routing system, your yields are much higher. Thus, you have a higher profit margin to work with. Its also considered "conservative" game play.
In a Continuation routing system (A-B-C-B-A) your per route yields are lower. Less cash flow on a per-route-basis. Continuation game play is also considered "aggressive". Because your basically invading another airline's hub. Which.. people don't seems to like.
Now, there are advantages and disadvantages to both styles of game play. Slot conservation, player image, airline stability and long term profit.
Generally, the most stable airlines are hub and spoke systems. Where a high profit margin is better able to handle unexpected events (ie fuel crisis).
Roughly, a continuation style will provide more slots for use. Thus, doubling your profit potential. While conservative game play produces higher yields, Continuation provides more profit by volume. So.. 20% profit margin of 100 million is good. But its not more then a 10% profit margin of 300 million.
Not to mention using Continuations is looked down upon. Your likely to be the poster child of someone's angry forum rant/crying by using this style
Both offer rewarding game play and take several games to master.