Opinions are mixed on this one, there have been similar discussions in the past.
It depends somewhat on the level of play of the teams. Some Legion teams are very strong, face good competition. Others are pretty weak and either face other weak legion teams or get pulverised the whole season. But for the most part a Legion team plays predominantly locally. For some people, Legion is a more economical choice, as travel teams can be expensive.
Travel teams also run the gamut. There are all sorts of travel teams that have started up. Some are nothing to write home about, while others are powerhouses who play good competition and play, as you mention, at good tournaments like East Cobb and other high profile tournaments.
If you can get on a really good travel team, I think that would be a very good thing. My son has been on very good AAU travel teams for a while now, and we'll most probably continue this route when the Legion/Travel decision needs to be made.
Also, don't overlook the showcases. If you attend some of the better showcases you can attract some notice as well. This has been a good choice for some players.
You should look through some of the articles on the HSBBWeb 'Main Web Site' and also do a search of topics here on the message boards. There is a ton of good info from people here that will help you.
Good luck!