Understanding 3 sensor design

From an image perspective, the beam splitting does not change the effective sensor size. Meaning that if you have a 3 sensor design with three 1/4.1" sensors, the camera will create an image with the same depth-of-field and field-of-view as a single 1/4.1" sensor with a color filter behind the same lens. Using a Bayer color filter reduces the effective resolution of the sensor, so the image created by a single Bayer 1/4.1" sensor with 4m pixels will have less measured resolution than the image created by a 3 sensor design with three 1/4.1" sensors each with 4m pixels. However, when the image from the 3 sensor camera is converted to 4:2:0, it looses color resolution anyway. If the camera provided the full 4:4:4 signal from the sensor, then the 3 sensor design would capture more light than the optically equivalent 1 sensor design with color filter.

In the real world, you're seldom given the choice between three and one sensors of the same size and same resolution at the same price (in which case the 3 sensor design would be superior). Instead, you're often faced with a choice between three smaller lower resolution sensors and one larger higher resolution sensor at the same price, in which case the choice is more difficult. In that case, the measured resolution and low light performance of the two different designs are empirical questions, meaning you'd have to test the cameras to see which was better. The field-of-view and depth-of-field also depend on the lens, so the camera with the three smaller sensors could produce an optically equivalent image to the camera with the one large sensor if it had a sufficiently brighter lens.