Should be fine to polish as soon as it comes out the bodyshop really, no advantages leaving it afterwards. In fact, most bodyshops polish surfaces up once they come out an oven...
Think both are pretty much of a muchness, otherwise wait a bit or the new Meguiars one maybe, although its not been tested yet, I can't imagine it will be bad. If we can send men to the moon in 1969, use satellites to track a persons movement to within inches, I am fairly confident someone can make a decent spec polisher, which is in essence just a modified sander/grinder...although I could be proven wrong!