domain name dillema ...

My competitor has a local "business.com.br" adress, the "business.com" and "business.org" are still available! What would be the best to buy in this case an .org or .com adress, knowing that i have to beat him in the local .com.br market?

Another dilemma:

The "business.com.br" has a famous event each year, let's call it "event.com.br" would it be better to buy "event2011.com" or "businessevent.com" ? Like this i can use the domain the next year, because the adress "event2011.com" would be useless afterwards...

.com 100%. for the second one can you spare $10 extra and buy both domain that way you got both sides covered and not having to be worried about losing traffic.

Ok, thanks for the quick answer, i have seen something on a post yesterday that .org would have a slight advantage on a .com

.com is easier to remember in my opinion.
go with .org if what you are planning to do is gonna be organization type not niche based selling products etc.

just do it. It is solely up to you making one of them better or worse.

I always think that .com is the better choice if you're going to have a branded website. In other words one that many people might type in the browser address bar directly. For ranking a .org has a slight advantage, but that advantage can be overcome with a good SEO and backlinking strategy.

If it were me personally I would buy both, unless they want a premium price for the names. I do that many times, I'll build the .org and take advantage of that slight advantage, and then use a 301 on the .com so that if anyone remembers the name but forgets the .org part, they'll type .com and still get to my site. I do all the SEO and backlinking for the .org site. It really all depends on what you want to do with the site.

As far as the event2011 vs. businessevent the same thing applies, it depends on what you want to do with the site. Domain names are so cheap that it doesn't hurt to get a date specific site for a lot of things, but then if you do a lot of backlinking you may be hesitant to abandon the site later. In that case the businessevent might be the better choice. Like I said it all depends on exactly what you plan to do with the site.