It's an interesting philosphical question. I would say good on you Ultralights - keep using those printed checklists. As you said, if it's good enough for a 747 crew...
That said, there are times in a single pilot operation when it's simply not appropriate to be reading checklists and this is where pnemonics come in.
In essence, in non-time critical situations, or in a situation where adequate "crew resources" are available to you to monitor the aircraft and the checklist simultaneously I would always use a printed checklist.
In time critical or high workload situations there is scope for the use of pnemonic procedures rather than a written checklist.
Interestingly, airlines have many procedures that are used by crew to configure the aircraft for takeoff and landing that are expected to be known by rote by the crew but only the things that can kill you really easily are on the printed checklist.