There are several reasons to not want a Diamond saber, besides price. Some people have no interest in color changing sabers, they just want single color sabers, with or without sound. Some people aren't keen on how you have to rotate the saber to cycle through fonts. And, there's one advantage to Emerald that actually makes Ultrasabers unique among saber smiths: you can get a color changing saber without sound. You don't have to get an Emerald and an Obsidian, you can get one or the other. Some people don't actually like sound sabers.
Now, if you want color changing and sound, Diamond makes the most sense. You get more fonts and other features, including up to 3 different colors per font. With Emerald, you have to plug it into the computer to change colors. And, on the subject of computers, the mini USB that Obsidian and Emerald use doesn't play nice with all builds of Windows 10. (the build on my computer, for example) Diamond, on the other hand, uses a micro USB, which uses the USB 3.0 standard, which is much more Windows 10 friendly. So, for those reasons, Diamond makes more sense than Emerald and Obsidian.
I personally don't own any Diamond sabers and likely never will, but I'm also a DIY person. Ultrasabers doesn't sell a DIY version of the Diamond board.
Thanks scifidude79. You are right of course. If you don't want / need the ability to change blade colors on the fly, don't need sound, don't need to change fonts, etc., there would be no reason to go with the Diamond Controller.
I should have been more specific, as I do enjoy all of that immensely. My primary inquiry had to do with Diamond vs Emerald w/Sound on comparably equipped sabers otherwise. I just grabbed a Dark Graflex, and ultimately went with Diamond. However, I had it configured with Emerald with many of the same options and in the end; it was only about $20 cheaper than the Diamond configuration. That seemed odd to me.