Actually, you are correct that deciding whether to use a MasterPage or not depends on the design and on the possibilities for future extension of your system. That is why we cannot give you a proper advise for this because we cannot predict the your future development. However, I believe that in case you do not intend to have more pages with the same template it is better to keep the simpler solution without a MasterPage. Also, in case it later turns out that you need to change the layout to use a MasterPage and you experience problems with the RadControls, you can rely on our help to get the desired result.
the Telerik team