If your content is located on a server that discounts a lot of output types. If you have users using mobile devices you'll either want to look into the new functionality added to RoboHelp 10 that specifically allows you to output for mobile devices or organise your content in such a way that it is usable on mobiles. This may well mean having different versions of your outputs.
The choice of which output you go for is largely arbitary according to your requirements. WebHelp would on the face of it be a good choice as would FlashHelp of AIRHelp. There are differences between them including how they are produced and maintained. Those are certainly factors in which one you choose. No doubt you'll have read the various sites that outline the pros and cons of each. The issues of Flash on Apple devices may discount FlashHelp for mobile devices. The fact that AIRHelp is non-platform specific may count it in but there are other issues with it.
I'm not sure if this is helping much. Each output type can be used but each has its pros and cons. It is very difficult to advise on which is best for you and your users because we do not know your specific requirements.
I have added a new Snippet on my site. See Item 33 at http://www.grainge.org/pages/snippets/snippets.htm#miscellaneous
It's a first cut and will stand some more information being added. Perhaps your feedback will help with that.
See www.grainge.org for RoboHelp and Authoring tips
BB AIR also uses Flash, so it's a no go for mobile devices.