I know I'm late on this discussion--It's hard to keep up--but I have two main thoughts on the Chicago/Johnstone style conflict:
1) It's good to do both. This has been my motto of late. Both have plusses and minuses and can add to your enjoyment and skills as a performer.
2) When they are well done, it's hard to distinguish between the two. Story/Plot vs Relationship/Character/Theme -- when it's a great show, it has all of those things. Great stories have great Relationship/Character/Theme and great Relationships/Characters are good stories in that they change and move forward. A false dichotomy.
Although when each form is done poorly, they suck in very different ways
Of course, my main two thoughts on the topic are in conflict, so oh well.