It would depend on what you are targeting

Dutch relevant site would be better with .nl

I think it depends on your target audience. If your website is written in Dutch and only targets people who live in The Netherlands, then by all means, you'll get better overall results with the .nl extension.

I agree with above, so long as you are NOT using both domains and pointing the the same site.

I think it would be fine to have the exact same website but an .nl version written in Dutch and a .com version written in English.

It doesn't count as duplicate content if they're in different languages. The duplicate content penalty only applies to a direct copy/paste of a large portion of text.

The domain extension doesn't have nearly the amount of power has people have believed, in my opinion. If you have money.eu or money.in or money.biz, you're still going to rank high if you have the backlinks to support it.

A larger issue with selecting your target audience is to think of where you want to host the website. Hosting geo-location plays a huge, huge part in search results.

A website hosted in the UK will always rank better in the UK than in the US.

I think domain name is not that importance to me. Its all about what you can do and what you have other than what you got.

I didn;t know this fact. Can you explain why is this.

well think about it. If a website is hosted in the UK, isn't it more than likely going to a website geared towards UK residents?

likewise it's the same for the US or any other country.

geo-targeting plays a huge role into search and how search results are display.

But overall, this is a great article that wraps up SEO in a nutshell.

http://www.seomoz.org/article/search-ranking-factors

I think the extension matters little if at all. I've experimented over the past 7 years with using domain names ending in .com, .biz, .net, and .org, and certainly my experience is that there is no obvious impact one way or the other from the extension. In terms of country-related extensions, I think that if the language of your site is French for example, then you will come up for french search terms, regardless of the extension. I don't think the extension is impactful personally.

eric,

you are right, extension does not matter, if at all, but location does. hosting location is a huge part of it.