That is like saying "which is better, a Chevy or a Ford?" It depends more on how it was done than what was done although I doubt that deionized water can equal well distilled if you are looking at the absolutely pure water.
Thanks rlm. I'm a complete beginner; would using deionised water instead of distilled water for cleaning damage the coin noticeably more though ?
What I am trying to say is the it is not whether the water is deionized or distilled, but how it is processed/made. Either can be the better choice or a worse choice depending. Use either one.
Acetone first. Distilled water second. Just dont clean them, if you mess the cleaning up you can cut the value of a coin by 90%.
It really depends on the coin. Since this is posted in the Ancients & World forum, I'll assume its an ancient coin, in which case deionized or distilled water shouldn't make too much of a difference.