I have Meprolight on most of my Glocks, but have owned a few used Glocks that came with Trijicons, and one new one. Of those two choices, I prefer Meprolight, for two reasons.
First, I'm not a huge fan of the white rings around the vials on the Trijicon sights. I don't think that sight dots (painted or illuminated) should be used at all unless it is too dark to see the outline of your sights (and I must disagree with Steve here; there are MANY common situations where you can I.D. an intruder/suspect as hostile even though there is not enough light to see conventional sights, such as a person advancing on you through a well-lit area and into a dimly-lit one), and for that reason, I find the white rings on the Trijicon sights distracting. The Meps dots are very low profile until you aim under low-light conditions, then if you find it is too dark to use the edge of the sights, the glowing dots are right there. This is a personal preference, and I know other folks who I respect that feel exactly the opposite.
Second, I've installed many sets of both types of sights, both for myself and others. Certain aspects of the construction of the Trijicon front sights leads me to believe the Meprolights might be more sturdy/durable under certain circumstances.
I have several sets of Meps that are approaching replacement time (been in continuous use for 10-12 years), and are still very usable. I have never had a problem with any Meprolight sight breaking or losing illumination, despite being knocked around rather severely in a few cases.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)