Thanks much to everyone here. So, I see that the 2mp is best for low light. Are we talking about this one (US Model)
N24BG52 by chance?
IMO, very few folks here have US models. It took Dahua forever (and a day) to make Starlights available via the official Dahua US channel (whereas folks here have been buying <mostly through Andy, @EMPIRETECANDY> the OEM international models since fall of 2016)... and the official US models are usually priced a lot higher than the OEM international models.
The usual reason folks usually want an official US model is to be eligible for support directly from Dahua. But there have been enough posts here where Dahua referred folks with US models back to their reseller for support (i.e. didn't offer direct support) to make it questionable if Dahua will ever talk directly to a consumer. These are not consumer-level cameras...
Or is the IPC-HDW5231xx from Andy better in one or more aspect?
The HDW5231 (via Andy) is a vari-focal camera. Once you mount it, you're able to electronically zoom the focal length between 2.7mm and 12.0mm, until you have the perfect width for your shot. The N24GB52 is a fixed lens camera. Once you mount it, the width of the shot is not changeable. Most fixed-lens cameras come where you can choose a focal length (typically 2.8mm, 3.6mm, or 6.00mm) when you buy it. You pick the one that will give you a width closest to the width you want, and that's that... no changing it... if it's slightly larger, you end up recording pointless stuff, like the side of a wall. if it's slightly smaller, you miss recording some stuff that would be useful. Although you can change the zoom (focal length) of the 5231 at anytime, it's not designed to be a day-to-day PTZ. You have to manually pan and tilt it yourself when mounting, and the zoom is really only designed to be adjusted occasionally (i.e. for some reason, the width of your scene needs to be changed).
Also, if I end up with the 2mp camera will I be disappointed with the daylight resolution? Is there a happy medium?
To me, this is how your MP question pans out:
2MP Starlight = great during the day, excellent (the best) at night
Higher MP camera = up to excellent during the day, poor at night (static shots may look OK, but movement almost always turns shots into unusable blurs).
You can actually "see" the differences for yourself at
IPVM Camera Calculator V3
Type in your address, pick/drop a camera onto the map, and then move the little guy around and see what the expected image quality would be.