I don't have much to say about whether or not to get a helmet with a brim, as I've only had helmets without one.
I think the main point to keep in mind is that the reason those of us who wear a helmet, wear a helmet, is to protect our most valuable asset... our brain. That being said, look for a mult-impact helmet. A good example is POC (I wear a POC Receptor Bug). The reason a lot of racers wear POC is because they are great mult-impact helmets. I'm sure there are other mult-impact helmets out there, but I trust POC from past experience and haven't found anything that I like better from an overall perspective.
Beyond protection, the POC helmet I wear is also comfortable, has vents for warmer days (I can remove a small liner that allows it to breathe better). I believe POC makes a couple versions with a brim as well. The only issue I have with my current POC is my goggles (Smith I/O) don't fit as nicely as I'd like.