walter,
For the Berbee you use the phone services for the app. there are a good few options that you can allow or diallow, but basically, you press services, "paging" and he group and just page. you can have multiple goups or one big group accordingly. you can also send text as well as pre-recorded messages (text and/or audio) Note you must have multicast working properly for the audio.
the phonetop is simple and its just to install the application. phonetop also comes with a survey application that you can push to the phone. i personaly like this feature.
for my customers, its all according to the environment
Phonetop - cuistomers that require the paging and a bit more
Berbee - same as above but has IP speakers to reach persons in noisy environments
each of these solutions has demos that you can download and setup. i suggest you try both and see which one you might be comfortable with.
