buykeyword.com or keyword.com?

Hello, an experienced seo person please explain to me, why buykeyword.com is not better than keyword.com to register?
what are the possible pros and cons?
I think pro could be that the buy keyword domain ranks higher for buy searches, am I right?
I can't think of any cons, but it is suspicious that seemingly noone uses them, or I just haven't lurked enough to see it...?

From the EMD update last year i would stay away from emds
But if you are really looking to go after emd then go for buykeyword ie., try to have the exact keyword in your domain name as much as possible
Hope that helps !

the reason I started to like emd is I have a blog, which only ranks for first page / 3rd position for the exact same phrase as the domain name (but with spaces included), for everything else the page results are abysmal, which I don't mind too much as it is just a test blog, but this is an important question for my new site

I still see EMD's ranking in my local niches , so that shouldn't bother you .
I would go with key.com just my personal preference.

Don't put words like "buy" or "purchase" in your domain names. Those words scream "affiliate site".