For presentations, screen sharing is important as are granular options such as the ability to share just one application (Microsoft PowerPoint, for example), document, or image or share your entire desktop. Most of the video conferencing services in this roundup also offer a whiteboard tool, which you can use to sketch out ideas or take notes during the meeting for everyone to see. You also need to consider what the participants are able to do, such as share their screen, enable their webcam, sketch on a shared whiteboard, and even take over the presentation. Think about how much actual collaboration you'd like in your meetings.
Other features I look at include the number of participants allowed on a call and the number of video feeds allowed simultaneously. The most generous is Adobe Connect, which is unlimited, but some offer as few as four participants at a time. Consider how important this is to your company. Most services let you record meetings, and a few let you edit the recording right within the software. These recorded meetings can then be used for your records or as webinars for anyone who missed the meeting or for new employees.
Once you have found packages in your price range, the most important consideration is ease of use. Obviously, if the user interface (UI) is difficult for you and your colleagues to navigate and use, then it's going to cause delays in meeting start times, which will frustrate everyone. For each review, I discuss the ease of signing up, creating a meeting, inviting participants, and setting up audio and video controls. I also look at the user experience (UX) from the meeting invitees' point of view, which can make or break a meeting.