Hi Barbara,
Indeed, the choices are many when it comes to choosing a Webinar provider.
You've got the more feature-rich and expensive players like
WebEx and
Adobe Connect. And then you've got the more affordable solutions like
ReadyTalk and
GoToMeeting.
All of these are good tools. The best way to choose the one that's right for you is to visit the vendor's site and match up their features against your own requirements and those of your audience. For example, you already know that PowerPoint and audio support are must-have features for you.
Helpful tip: Ask yourself what additional requirements -- your own requirements AND those of your audience -- will be key to the success of your Webinars.
Below is an article by IdealWare that includes some evaluation criteria for choosing a Webinar tool:
An Influx of Webinar Tools
Hope this helps.
Yann