Both are valid. My preference is EE. I can sacrifice some pacing for more detail. It's time well spent. That said, first viewing? I quite liked the opportunity to watch these films again, but extra. Can't do that if you start with the extended versions.
If the person watching is the kind to enjoy an extended edition, I reckon they'll seek it out more often than not. Likewise, a bunch of people will not care and the theatrical will suffice for them. That one is probably the easier to see which is ideal.