One of the claims made for the KDE 3 series is that it has more options for personal preferences than the KDE 4 series. This claim is hard to examine, because the KDE 4 releases began with few options and gradually added more. To complicate matters even more, KDE 4's System Setting window was extensively revised in the first few releases, although recently it has become more consistent between releases.
In addition, KDE 4 tends to minimize top-level menu items, while KDE 3 was more likely to add them. At other times, it seems to have dropped options that most users are unlikely to use. Consequently, while Trinity at first glance appears to have more options, in many cases it has simply organized the ones it has more loosely than modern KDE does.
Nor can you always make a direct comparison, because each desktop has options that only make sense within its own context. For instance, the Removable Dialog settings is only applicable in the context of modern KDE's Device Notifier for external hardware.
Even the layout is not a major difference; KDE displays choices in groups of icons by default, but you can easily change to the tree view of Trinity's Control Center.
Verdict: Tie. I'm assuming that the choice between the System Settings and Control Center layouts is unimportant to most users.
System and Administration Tools suffer the same problems as personal preferences -- naturally enough, since they appear in the same windows. However, Trinity has specific controls for peripherals like Joysticks and PCI Cards, as well as more displays giving information about the computer hardware and configuration and useful options such as a default spell-checker that KDE lacks.
Verdict: Trinity. Average users may not notice such lacks, and administrators probably leave the desktop in favor of the command line. But, for intermediate users wanting to learn how to manage their system, configuration and administration tools remain KDE's largest lack.
KDE 3.5.10 was the last in a series of thirty-five release stretching over eight years. With this history, it had a reputation for being extremely stable and crash-free.
However, while Trinity's latest release, version 3.5.13, suggests a continuity, the continuity does not necessarily include stability. On my machine, Trinity has frozen several times, including once when I attempted to change the menu, when the only recovery was to delete the Trinity folder in my home directory. Similarly, changing the theme spontaneously adds a panel on the left side of the screen, and using the Monitor & Display to change the resolution causes it to crash without making any changes. In addition, twice in about thirty logouts, Trinity has hung.
In comparison, I have installed KDE half a dozen times on different computers, and twice as many times virtually, and never had the slightest problem in four years. The most I can say is that modern KDE runs best with at least two gigabytes of RAM.
Verdict: KDE. I have heard of difficulties with KDE, but never experienced them.
Before sitting down to this exercise, I assumed that KDE would have a large lead. I was never a fan of KDE 3, and I assumed that, for all Trinity's heroic efforts, the passage of time would not have been kind to its foundations.
The results, though, surprised me. Awarding one point for a win in each category and two points for a second place finish, I find that I've given KDE a total of 11 points, and Trinity 12 points -- technically an overall win for KDE, but by most standards a tie.
What is useful about this exercise is that it points to the strengths and weaknesses of each desktop. It allows the cautious confirmation of the myth of Trinity's speed, and a debunking of the myth of its stability.
However, each of these categories should probably not be given equal weight. Personally, I'd like to see proof of Trinity's increased stability before relying on it. Nor am I sure that, having adjusted to using KDE's Activities, that I'd like to work for any length of time without them.
Your priorities may cause you to give the categories different weights. But, if nothing else, the comparison shows that Trinity can still function as a modern desktop, and that KDE is not as a great a departure from the classic desktop as you might have been led to believe. Choosing between them may be a matter of tradeoffs, but, if nothing else, I hope I've given you the basis for an informed decision.