1 domain + keyword pages OR multiple domains

Title says it all. If I have 1 main keyword and 5 related longtail keywords, what you guys think when making decision how to proceed?

Those 5 related keywords are very easy to get #1 on google (at least on #1 page) with exact match domain. But with my main keyword domain it will be harder.

Depends on how you want to look at it, but the current trend is that EMD's are going to start carrying less (notice I didn't say none) weight in rankings.

Also, the domains aren't free. Do the KW's have the kind of marketable traffic to warrant their own site?

Personally, I like medium sized sites VS. lots of tiny sites (I find it easier to manage).
Without knowing search volume and competition this is mostly a matter of personal preference.

How much search volume you are looking for if the CPC is around 4€? Dont worry about competition, there really isnt any.

This is still bit of a question mark for such a newbie as I am.

Ive done onpage SEO now to my main site/main keyword. And I have allready done 4 subpages for the rest of my keywords also.

Still Im thinking I will do 4 EMD micro sites too. Is this a bad idea? And if I do this, should I do it like this:
EMD keyword1, subpages for kw2/kw3/kw4/main kw
EMD keyword2, subpages for kw1/kw3/kw4/main kw
EMD keyword3, subpages for kw1/kw2/kw4/main kw
EMD keyword4, subpages for kw1/kw2/kw3/main kw
?
Or should I just make just 1 page sites for 1 keyword.

And then link it from each micro sites only to main keyword domain, and then get a lot of backlinks to each of those micro sites?

Im bit lost figuring out what is the best way to go, so any help is appriciated