That $17,000 Apple Watch Edition you just bought might not be quite as good as the $349 Apple Watch Sport. Sure, it uses superior materials and it looks fancy. But, according to a new DisplayMate report, the use of sapphire crystal might hinder the wearable’s display performance in bright light, which poses a major problem on such a tiny screen. What good is a watch if you can’t see what’s on the display?

The good news is that no matter how much you spend on the Apple Watch, you’re getting a good display regardless. In fact, DisplayMate crowns the Apple Watch’s OLED screen as the best out there (for wearables), which, to be fair, is still a very small market. The study found that the Apple Watch “provides a very good color match to the iPhone 6,” displaying excellent color management, viewing angles, power management and brightness control.”

However, therein lies the problem—at least for Apple’s more expensive Apple Watch with sapphire crystal.

Sapphire reflects about twice as much ambient light as glass (due to fundamental principles of physics and optics). Since any reflected ambient light decreases image contrast and color saturation, displays with sapphire can’t perform as well as the lower reflectance glass in ambient light.

Apple’s Sport model comes with Ion-X glass, which is much less reflective. If you were to compare the two in an outdoor setting, you might find that the Sport model is easier to read, DisplayMate’s analysis found.

Again, Apple’s new smartwatch lineup is identical in terms of functionality, only differing in the materials used. While the Sport model might not initially sound as luxurious and fashionable, it could wind up being better in the long run—something that’s definitely worth taking into consideration.