I believe your business requirements will drive the answer to the question. Both IP and FR provide an excellent platform for data and voice communications. The difference would be the cost you are willing to incur. IP is easier because it is more popular, and there are more systems now in place. FR offers a great flexible package as well.
Remember, each will use the same connection type, and both require specialized equipment to allow data and voice at that same time. I don't think either is better than the other. I like IP simply because you can be more flexible with your security solutions with firewalls, encryption and IDS. There are only hardware encryptions with FR, but IP offers much better solutions.
For more information on this topic, visit these other SearchSecurity.com resources:
Best Web Links: Virtual Private Networks
Webcast Archive: Build-it-yourself VPNs
Featured Topic: VPN security
This was first published in August 2002