It's a draw
We've had close votes before, but this was the first time in Great Debate history that the audience was evenly split. And perhaps, we shouldn't be surprised. Deciding when and how your company should upgrade its tech, whether in the data center or on the desktop, is a choice driven by the specific needs of your organization. There's rarely a one-size-fits-all solution.
As David argued, overhauling your data center can pay dividends through energy savings, improved processing performance, faster delivery of capabilities, and a shorter period to achieve measurable ROI. But even he acknowledged the higher upfront cost. Adrian outlined the benefits of incremental updates--lower upfront cost, less likelihood of a service disruption, and the ability to focus IT spending on the systems in most need of an upgrade. Yet, he still believes "that a time will come when almost every company will need to consider a total overhaul."
Given the audience's split vote and the debaters' acknowledgement that both choices can be correct given an organization's specific situation, I don't believe there's a "winning" side to this argument. I judge the debate a draw.
Updated April 4 3:15 EST: When I submitted my final thought at 11:30 EST on April 4, the vote was still 50% Overhaul and 50% Incremental. In fact, the percentages hadn't moved since the previous day.
Despite the "incremental" side taking the lead after a few late votes, my mind remains unchanged. As Adrian noted, if your datacenter looks likely something from the Flintstones' era, it's time for an overhaul. On the flip side, I don't know any company that rips out its datacenter and starts over from scratch every year.