I read both. I have to admit I was never much of a fan of Asimov's non-fiction or work outside of SF... I could take it or leave it. I do find most of EVD's examples to be ridiculous... The Nazca lines, for example, were clearly never landing strips, for a variety of reasons, although they may have been meant to be seen from above.

What Von Däniken did teach me as a child was to have a sense of wonder about the ancients and their achievements. Maybe not spaceships and electricity necessarily, but their feats of masonry and sculpture. I've seen dolmens capped by stones the size of a bus, that I felt uncomfortable walking under, even though they had managed to stay like that for thousands of years. We struggle to replicate some of these things today yet they apparently did so without metal tools, proper ropes or any number of other things. The planning alone would have taken many years.