Hi Derek,
Below is a link to a whitepaper your organization may find helpful when choosing either one or both Microsoft Web conferencing solutions.
http://www.microsoft.com/downloads/details.aspx?FamilyID=250c2446-14dc-4f16-8c0a-38a0aad055b2&DisplayLang=en
Also, here is a good page on the Microsoft Office Live Meeting site with a table that shows a feature comparison between Live Meeting Standard, Live Meeting Professional, and Office Communications Servers 2007.
http://office.microsoft.com/en-us/livemeeting/FX102407251033.aspx
For more information on Microsoft Office Live Meeting hosted and on-premise Web conferencing solutions; I recommend to call a Live Meeting Sales Specialists at (866) 463-3866. They can assist in choosing the best solution for your company.
TD