In my opinion, Showtime is easier to use. Also, there is a lot of content already out there for Showtime. LSX will only have a few demo modules with it; beyond that, you'll be on your own.
LSX can do some really mind-blowing stuff though. (3D warping, 3D wrapping, intricate transforms, abstracts like you've *never* seen before, and incredible effects that can be programmed to do literally anything you can dream of.) And in that respect I think it's probably more versatile than even Showtime is. It's also considerably more affordable, making it very attractive to the hobbyist who is looking for the most power for his dollar.
The procedural effects in particular have to be seen to be believed. However, you really need a solid background in either mathematics (algebra and trig) and/or simple computer programming in order to really unlock the power of these expression-based effects. So yeah, there is a definite learning curve with LSX, and it's much steeper than the one for Showtime.
One big difference between LSX and Showtime is that LSX offers is the ability to stack multiple iterations of even the most simple effects (without diving into the complex expression editor at all) to create hybrid effects that are very intricate. For example (keeping it simple here), you could have a rotate about Z effect, and then add a second rotate about Z effect below it and a little later on the timeline. This would produce a "speed shift" when the second effect started.
To do this in showtime, you have to replace the first rotate effect with a second one that has a higher speed, because you can't have two effects that do the same thing active in the same track at the same time. But in LSX, you can have as many effects as you want (up to the limit of your computer's memory), so there's essentially no limit to how deep you can stack effects.
Some people might prefer Showtime's standard of only having one rotate effect for the track, and I can see how that might actually be preferable for a professional show designer who is following a script or a storyboard. But I have often wanted the freedom to stack effects in order to create new visuals, without having to calculate ahead of time exactly what combination of settings would be required to pull it off using just a single effect.
Where this "effect-stacking" really shows it's power is when you start combining move effects with rotate effects and color effects, all while the frame is being drawn. It's fairly simple to turn a circle into a cross, or an octagon, or some wavy abstract shape that has no name. Add some point-count-based color effects and you've got a flying, wispy line that curves through the air, trailing a blaze of color that slowly fades away as it moves. You've got to see it to believe it...
There are some quirks to the LSX interface that you'll need to get used to. One is that the navigation buttons are spread out among three sides (top, left, and bottom) of the main window, and some of the most common controls (play, stop, pause, zoom, etc) are located at the bottom. Also, the frame list window is not normally open while you are working on the timeline, which is different from the way most people use Showtime. Still, these are minor differences that most users will quickly adapt to.
The effects editor is very daunting the first time you look at it, and it might actually scare some people off. By contrast, Showtime's effect editor is a lot easier to grasp when you first load it, and overall I think that Showtime is more user-friendly that LSX. But what LSX lacks in ease of use it more than makes up for in raw power. Even with the built-in effects, you'll be amazed at what you can do with the software right out of the box.
Hopefully there will be some video available soon to showcase some of the power you can unlock with this software.
And in closing, I agree with Steve: LSX is valuable even if you already own another laser show software package (including Pangolin's LD-2000 system), because of the versatility of the effects editor as a frame-creation tool. I think a Basic license for LSX would nicely compliment *any* laser show software suite.
Adam