just add my comment as a hobbyist who has tried both
On my 24 inch cube I needed 2 Ai Sols and even then there was no light overspill. If you want to see back up of this please look at my tank build thread
http://www.canreef.com/vbulletin/sho...t=60988&page=8
Things move on fast in lighting in 18 months!
On the same tank I am running 1 Radion with slight light overspill.
When you take into account the need for 2 Ai for one Radion the price no longer becomes a bargaining factor between the two
Yes i have seen one SOL on a 24 inch cube but the lamp was high and there was no real value at sand level.
Just my 2 cents.