The biggest reason to do your layering in UF rather than PS is that the way you have to do it in PS is VERY clunky and odd compared to doing it in UF. In UF, you can just hold down "Control" and move your mouse in the window and the selected layer(s) moves, hold down "Shift" and move the cursor and the layer scales larger or smaller, Hold down "Alt" and the layer(s) rotate and/or hold Shift along with Control and you can stretch/skew the selected layers. With PS you have to go thru all that Edit/Transform/Scale/Rotate/Skew, etc amd "accept" the changes each time. VERY click-intensive stuff. Not to mention that layering is what UF is all about and all of your layers are in the right positions in relation to each other and you can see real-time what you are doing. To make each layer one at a time and export to PS would take a lot of time. I know because I had to do a bunch of re-stacking of layers to rebuild my "Soulseed" image when I wanted to render the egg with anti-aliasing separate from the flames. Luckily, I could just resize the flames from the composed image in UF to my final image size and then export them as .png's with transparent backgounds and they pasted into the final sized psd window in the exact positions they were in in the original composition. I DID help to be able to use the Eraser tool on the unrendered flames, though.

Making mask layers is MUCH more capable (at least at my low level of "expertise") in UF than PS because you have control over the opacity level/slope of even the tiniest areas of a layer by using Iteration or Angle coloring and the Color Density to isolate the unwanted parts. I've made a mask in PS but only by using a shape with a transparent background that I'd already made in UF first.

The color controls that PS has are very rough, gross change tools that don't allow you to change just one color or area of a fractal. They affect the entire image. With UF, you actually "paint" the fractal. UF also has many "filters" in the form of mapping transforms (spheres, planes, kaleido's, tiles, etc) and you can make many more and specifically tailored textures in UF by using one of the "Pixel" programs and one or more of the many coloring algorithms that are known to be great for texture pattern making. The filters PS uses for that stuff are all fractal-based anyhow and with UF you can make EXACTLY the texture you want and not be limited to the settings a filter has. I will say, though that the Flaming Pear "Flood" filter blows UF's "Lake" effects away at least as far as "realism". I've found a mix of the two effects, overlaying a "Laked" layer onto a "Flooded" layer,  to be pretty cool.

In the end, though, I reckon it boils down to what one is most comfortable/experienced using. Sheesh - I oughtta be a UF salesman! There's LOT's of ways to skin a......er.....fractal - lol!

And thanks, Damien, for the Celeron props - I know you already told me they would be ok but somebody on the Apo list made a crack about "celery chips". I'm sure you are more knowlegable.

Rick