I use both and to be honest haven't had problems with either. I often choose lrf because I don't like the page numbers in the right margin that you get with epub.
I'm not too worried about future proofing as tools such as calibre allow you to convert one format to another, although I have to admit that so far all the books (about 10 out of 300) that I've paid for are epub. I do have secure lrf files but they were all free and mostly PD so I should be able to get hold of alternative formats if I need them.
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