The more unusual or resource-intensive your method is, the less likely the spambot authors are to bother about it. Using a plain mailto: link is just asking for trouble though. I suspect although spelling out the words or using HTML entities is better, it's not that much better, as it's easy for a program to substitute strings. The more obscure methods probably work well for the reasons stated above.
Of course, there's no way to communicate any piece of information without making it understandable, and on that basis, any address you put on line could be read by someone and passed on. You can't publish something online and keep it secret at the same time. You can only take sensible precautions.