Subdomain or new exact-match domain?

[PDXOR]

Yo SEO gurus -- if I am breaking into a new niche, which is considered best practice if I want to rank?

1) Create a subdomain www.mydomain.com/newniche/exact-match-KW

or

2) Create a new domain www.exact-match-KW.com

The existing domain is <6 mo's. old, and the new niche isn't related to the current content (but would make sense thematically).

Thanks --

 

[AMagz]

I would go with http://www.exactmatchKW.com and start fresh, since the other domain isn't all that old, and the content would be unrelated.