I have a offlineMapVC and a onlineMapVC for my application to support both online maps (using MapKit and Google Maps) and offline maps (using Route-Me).
I made my own mapVC to manage the switching of these mapVCs and be able to use the view controller as one separate view controller. Well I've done this by making the offlineMapVC and the onlineMapVC instance variables of the new mapVC witch I now use all over my application.
First off all things seem to work but. However while using this approach for a longer time I ran into some problems due my using of View Controllers in a hierarchy. I read this is the wrong way to go. What is the right way to manage the switching between two view controllers? My question seems fairly simple but I couldn't find a decent solution.
I put view controllers in view controllers, myself, and I have seen much better programmers than me doing the same thing. (See Rob Napier "iOS 5 Programming - Pushing the Limits". He mentions it frequently.) As long as you don't have more than one view controller directly controlling the same views and subviews, you should be okay with it.
Since Jonah Williams wrote that article, I think iOS 5 formalized the use of view controller hierarchy with custom content view controllers. You might consider your mapVC to be a custom content view controller and implement onlineMapVC and offlineMapVC as child view controllers.
(Apple documentation links tend to change frequenctly, so Google "Custom Content View Controller" for the documentation.)
If you can give some more context to what you mean by "switching between two view controllers" that would help answer your question. Generally, I have more than one view controller active at the same time. I don't switch between them. (I use navigation and tab bar controllers in the same applicaiton, but I assume you are aware of how those work and you're asking a different question. It's just not clear what the detials are in your case.)