If you want to stick with Tamiya paints, I would say either is fine, even mix both together and try that. The "dark yellow" though was only introduced in February '43. The desert yellow I would say is more of a british colour, but the DAK did use captured stocks. If you can afford the spare change, do yourself a favour and try some of Testor's Afrika Khakibraun `41, Afrika Grünbraun `41, or Afrika Braun `42.