Dealing with comments

I love blog comments.  But what's the polite way to respond?  A reply comment, or an email?  Which would you prefer?  I like the email reply, but I don't always get to everyone who comments, and sometimes you need to answer a comment's question on the blog.  Please drop me a comment and let me know.  Thanks!

(I tried putting a poll on here but they either didn't load, or the results page was full of unsavoury ads.  So I'm doing it the old fashioned way)