Bellucci gave a good account of himself at Indian Wells, taking Federer to three sets in the 4th round after getting lucky with his draw, drawing Rosol, a sick Melzer and having Davydenko withdraw sick in R3. Before Indian Wells his season had been very average. Gil made the second round at Indian Wells as a LL and played a competitive match with Isner in the second round. Bellucci made the third round here in 2010 and should have a lot of crowd support in Miami. Gil made the third round at Miami in 2009 after qualifying and won a match here last season.
Overall, Gil's had the most impressive result of the season between these two, making the third round at the Aussie Open. They've played once, a 7-6 7-6 win for Bellucci in Costa Do Sauipe in 2009. I don't really think last week is any indication of Bellucci's form. He got a lucky draw, and this is a totally different situation. Bellucci rarely puts back-to-back good weeks together. I predict Gil to win in three sets.
Bellucci did make the semis in Sao Paulo as well, even if it wasn't much of a task to get there. Regarding Indian Wells, I don't think you can really dismiss a result as 'not-indicative of true form', because form is predominantly mental anyway. Pushing Federer to three sets could easily put Bellucci in good form. Of course, Gil is always going to be the more consistent player between these two, but the minute Bellucci hits his stride, Gil will find it hard to hang in there.
Gil only has one top 50 career win on hard (Petzschner in 2009), with the exception of an injured Granollers in Australia this year and Nieminen by retirement.