Actually I have a very similar issue, but already some data, that unfortunatly does not help me (as I just started with seomoz).
My issue is sub-domain, TLD or folder - and yes, brazil is one of my targets as well.
For European countries I had already set up subs and 1 tld where a sub redirects to...I know that i still got some work to do, so don't hit me for that - thats what I am here for
SeoMoz tells me this in the report:
Domain / Page Authority / Page MozRank / Page MozTrust / Domain Authority / Domain Moz Rank / Domain MozTrust
Root (.com) / 46 / 5.45 / 5.37 / 36 / 5.45 / 5.37
sub / 16 / 4.67 (all subs have this) / 5.09 (all) / 36 / 4.67 / 5.09
Genuine TLD (sub 301ed) / 31 (!) / 4.67 / 5.09 / 26 (!) / 4.67 / 5.09
This genuine TLD has about 8 times as much links pointing to it (its older and was "alive") as the subs have (so far), but it actually lacks domain authority while it outperforms the subs in page authority.
I'd be really one happy guy, if someone could explain to me the real pros and cons for the useage of subs, folders and genuine tlds per country for SEO.