I'm not really looking at this as Apo verses UF. You can't find flames UF. You must use Apo to find them. It's more UF verses layering programs like Gimp, PSP or PS. The advantage of using UF (once you have found a flame in Apo) is that you still have complete control of the flame gradient and iteration density. When you plug a flame into a photo layering program you have lost that complete control.