A removable visor is a great choice if you ski in varied conditions and want flexibility. You can snap it on for sunny days when glare is an issue, or when wet snow is flying and you want to keep precipitation off your goggles. Then just remove it when you don't need it—like on overcast days or when you want a cleaner, lighter helmet.
This feature is especially popular with freeride and backcountry skiers who encounter changing weather throughout the day. If you're hiking for turns, you might start in shade and finish in bright sun, so having that on-the-fly adaptability is really handy.
The main trade-off is that removable visors add a few moving parts and attachment points, which means slightly more complexity and a small weight increase. Also, double-check that the visor works with your specific goggles—some combinations don't play well together. If you mostly stick to resort groomers in consistent conditions, a fixed brim or no brim at all might be the simpler route.