What do you think about the SEO value in a domain name? Also is it better to have for example phuket-real-estate.com rather than phuketrealestate.com?

I think you should go with the flow

Buying a domain name is cheap. Get both.

It helps, but it's just a very small part of overall seo in crowded and highly competitive markets "phuket real estate" being an example.

Numerous domains pointing to your primary website. SEO is reasonably easy to do yourself with keywording etc. Check competitors sites that are ranked high in search engines and see what they are doing right click-view source. Don't go paying some muppet $$$$$ for something you can easily do yourself.

Both of those names contain the same keywords, so have the same value from an SEO standpoint. - Google doesn't need dashes to delimit words in a domain name

Further to this you mustn't undervalue the human element. People will forget the extra punctuation in a domain name and you have to say it when you say the domain name. Stick with the one without if you are only going to have one.

Two words always better than three