Being slightly pedantic I think the question:
So what is more important to you: downtime or data loss?
is wrong and not a reflection on the spirit of the article, more correctly it should be along the lines of:
So what is more important to you: downtime or partial/non-current data?
But, in answer to the spirit of the article, the answer is as always, it depends
. I can think of several of the systems I have written/support that could function on a partial, non current data set, and others that are completely dependant upon the results that have happened within tens of seconds before. I think the defining requirement is to understand how the customer works with a system and the impacts of all scenarios such that some form of SLA is in place which allows the most efficient and cost effective re-instation of a fully working system.