I've got 'em both, and there's no way to compare the two. Ever used Kai's Power Tools v5? It's a bit like comparing Frax4D with Fraxplorer with Fraxflame. If you haven't used this plugin I'll explain. They put all three Frax(foo) plugins in the same box because all are so diferent. So're XD and UF.

I guess the answer to your question is another one right back at you. What sort of work do you want to do?

Another consideration is whether you want to create something easily re-renderable (so you can make a larger version a year later when someone requests a print). As of this version XenoDream makes doing so a P.I.T.A. unless you keep detailed notes on each and every step you took to make the original picture. And even if you do keep notes, rendering it larger sometimes gets the colors messed up. However, if you've got the time and the storage space, render 'em huge to begin with and then just save the files on CD or something.

For what it does, XD is the best program around and I'm glad I bought it (or was gifted with it). I'm not dissing it at all! The three-dimensional objects/pictures one can create with it are simply awesome and just can't be duplicated with any other program on the market right now (though Z Brush can create superficially similar images).

One thing XD can do that UF can't is export objects in several formats that programs like Bryce can handle. I don't know a lot about this, though, as it's not something I do. This capability is supposed to be expanded in subsequent releases.

UltraFractal makes more "traditional" 2-D fractal images than XD does. It's very well supported, has scads of people contributing formulas, coloring methods and transforms to it (sort of like PS plugins), and does let you re-render small images to large ones without detail loss.

But what sort of art do you want to do? Some good examples of XD's capabilities can be seen at XenoDream.com or on the XenoDreamPix forum at Yahoo Groups. Examples of Ultrafractal work are all over, like here at Renderosity. Very different styles, no?

I'm sure Nahee will appear in this thread some time soon to give you his URL listing other programs that might interest you. I don't have it handy.

All the best!

• Sean