The problem is "all else were equal." They are not. Most cameras as the MP rise are relegated to the 1/3 sensor (with the exception of a higher end 3MP as noted earlier). The Starlights spread the 2MP on a larger 1/2.8 sensor or a premium model on a 1/1.7 sensor. That is where your biggest difference is, as the sensor grows, you gain more. Plus, each of those sensors is not a progression of the same rectangle dimensions impacting their vertical FOV, and it also impact the size of the lens which has to be larger for the crop factor to equal the same horizontal FOV but not provide the same depth of field and other characteristics of the same lens. In other words, a 3.6mm and 2.8mm on a 1/2.8 sensor (same as used in point-n-shoot cameras) has a crop factor of x6 and to obtain the same 87degree and 110degree hfov in a full frame 35mm sensor would require a lens 22mm or 16mm respectively, but it is limited to fov only as a 3.6mm lens will not provide the other characteristics of a 22mm (technically 21mm or 24mm as 22mm is non-existent other than an approximate zoom setting). Likewise with the 2.8mm and 16mm matchup.
Now to the other part of the question, more detail on higher MP. Probably yes is sensors are same, not cramming more MP on a smaller sensor - but all cameras are compromises and have tradeoffs. My avatar is a bit misleading as I have switched from the Nikon pictured, to Sony and currently shoot with a A7rII. The sensor, referred to as full frame in the digital world is physically the same size as 35mm film so there is no crop factor) is 42MP and was the first to use the Sony Exmore backlit technology in that size sensor that the Starlights do in the 1/2.8 sensor. Needless to say, on stills I can pull and extraordinary amount of detail out of photos (Canon shooter in awe, Nikon uses Sony sensors) but deal with monster 43Mb files in RAW and 7.5Mb in jpg which also impacts storage space. It does 4k video but was designed for stills. For video, the preferred model is it's sister, the A7sII (costs about the same) with the same size full frame sensor but a "measly" 12MP. It also has the older non-Exmore non-backlit sensor which expect will be upgraded when "A7sIII" is introduced. The A7s series was designed first for video, so the stills can't provide the level of detail that the A7r series or the 24mp A7 series can, but that is not to say it is bad. Likewise, the A7s series can handle video better with more filming (SLOG3 etc) options than the A7r series which tends to emit more noise in low light. - phenomenal, but not as good as the A7s in low light due to the MP density blocking light on the same size sensor..
In short, look at what the camera was designed to do and the compromises imposed as specifications change.
