www or no www?

It doesn't matter. Your site can either have www or no www. But once you choose which one, you should stick with it for the rest of the site's life.

I agree with your point of view.

Linking to both dilutes nothing (albeit that it's entirely unnecessary and silly).

It's linking to "either" that would dilute the benefit to the other. One is a subdirectory of the other (you could in fact have two different sites on them, if you wanted to).

It doesn't matter which one you use, as long as you build your backlinks consistently only to the one you're using.

The "www" part adds nothing and is completely unnecessary. On all my newer sites (since I realised this) I don't use it at all, and I just redirect the "www" one to the one without the "www". On my older sites, I have backlinks to the "www", so unfortunately it makes sense for me to continue using that one.

They are, and you've done to well to ask. I wish I had done, when I started. I'd have learned at an earlier stage that the "www" version is entirely unnecessary.

That's not strictly true - it won't "improve" your seo efforts, it will just shut one option you had for doing ineffective seo.

Technically it makes no difference which you use.

The only reason it's even a consideration is because if you don't realise that www and non-www are technically different you could accidentally build links to both, hence diluting the value of those links.

Since Google and most other search engines understand that this is a common issue - they will often treat them as one, and even provide a way for you to tell them which one you want them to use.

Whether there are other considerations for which to use is a different matter and you'd need to do your own research to work out whether your target market tend to prefer www or non-www. Some people just type in the domain name without even putting the extenstion, some people put the address exactly as they see it in your advertising, so whether it matters or not often is more focused on how you're marketing your site and where your visitors come from.

If you put www. on all your marketing material then it would make sense to use it on your domain. If you don't then it may be that more people type it without it and so you'll be slightly better off leaving it off.

Andy

Yes, there is more important stuff to fry, and it's a minor issue.

However, it's a minor issue you should be aware of and address each time you start a website.