I'll put it this way, MapTool can pretty much do everything that OpenRPG can do, and is growing on a weekly basis with incredible support and user driven features.

The group I joined a while back was using ORPG, but finally switched to MapTool and we haven't looked back since.

For VoIP, I highly recommend Ventrilo, and highly discourage the use of Skype. I've posted elsewhere the reasons for not using Skype so I won't post them here. Whether using voice or chat the games seem to go just as fast and we get as much done in both - barring technical difficulties that might crop up.