I am going to chime in here as I just went through researching and purchasing G5 Radions. As previously stated, Pro vs. Blue is a personal choice. I like primarily blue lighting, but liked the idea of going with more natural looking whiter light around midday. I think the Pro are a little more versatile and Ecotech provides Corallife templates for AB+ on the Pro that gets plenty blue. If you Google G5 Radion Pro vs Blue there are some youTube videos showing comparisons.
According to BRS, the maximum coverage is 32" X 32" and recommended coverage is 24" X 24", so ideally, you would need three. I have mostly softies and LPS so have been getting away with less than ideal and still not having them at 100%. If you have a lot of SPS I would go three, though.