EJ,
What it depends on is your workflow, and your needs during and after the edit.
What is your final product? Will it be handed to a studio for online editing? Will you get digital media from others who have already been editing with the footage? Will you have freelance editors to whom you send your footage and media?
If so, you definitely should consider the entire Xpress Pro family, including Xpress Pro HD and Xpress Pro Studio.
If your projects are totally closed loop, meaning you do the shooting, editing, output to tape or DVD and no one else is involved with your post production process, there is no reason not to consider Liquid. It has a robust and fine set of tools (some of which I hope Xpress Pro will inherit). It has a somewhat shorter learning curve, and the price point is nice.
Both product families will continue to be developed and supported by Avid.
I say this as am everyday Xpress Pro Studio Complete user, and my needs and interactions with other producers, editors and systems are aligned perfectly for the Xpress family.
Regards,
Cre8tive