I think it is sort of like dual channel and single channel. There are all sorts of "theoretical" advantages to running RAM in dual-channel architecture - but only in specific and tightly controlled scenarios. But in the real world, those advantages are rarely ever realized - much to the disappointment of RAM marketing departments. This is even true with faster RAM over slower RAM. The only consistent scenario for the vast majority of users when it comes to RAM is that more RAM tends to trump everything else. Of course there is a point of diminishing returns but generally speaking, adding more RAM is better, in terms of performance and bang for your money, than replacing existing RAM with faster RAM or by reconfiguring RAM from single to dual or unganged to ganged.
So unless there is really compelling evidence to deviate from the defaults, I say go with the hardware makers' decisions and defaults. After all, they want the majority of their users to get the most bang for their money too. This applies to operating systems and many other things as well. Contrary to how many feel about themselves, they are not the exceptions to the rule.
