The Chronicles of Narnia: by publication date or chronologically?

I didn't know this was an issue until last night. After enjoying Joanna (she of Turquoisia fame) in a musical version of Aesop's Fables at her elementary school, I joined the family for a cup of tea afterwards. We got on the topic of upcoming films, and of course "The Lion, The Witch, and The Wardrobe" came up.

Joanna's 14-year-old brother Alexander got huffy and said he was mad because they made LWW before the first book. So I sez, "What first book? I thought LWW was the first book." "No there's one before it (The Magician's Nephew)." So a discussion ensued about whether MN was a "pre-quel" like the Star Wars movies of late.

Well, nothing was settled at that time, but I did come home and Google the thing. Turns out that Alexander and I were both right. LWW was indeed the first book written in the series (1950) - in fact, C.S. Lewis intended the book to be a stand-alone, not realizing that he'd find a way to return to the story again and again. He wrote MN in 1955, but the book takes place before LWW and gives backstory, as it were.

Now Lewis aficianados are having the great debate over whether to read the books as written or in chronological order, putting MN before LWW. The "MN 1st" group says that chronological order makes more sense; the "LWW 1st" group says by doing that, the magic of LWW in particular and the series in general is dissipated. C.S. Lewis seemed to favor the chronological order, based on a letter written to a young reader, but he admits that he never meant for LWW to lead to a series and that books can be read in any order.

What do you think? It's been years since I read either LWW or MN, though I remember LWW much better than the other. So. By publication, or chronologically?