I see that the ebay price (in CAD) for the HDBW4431R-ZS (4 MP) is about $120, while the HDW5231R-Z (2 MP) is $270. Why would a 2 MP camera be more expensive than a 4 MP? Both are motorized varifocal, the 4431 has SD slot (I don't think the 5231 does). The 4431 is dome (this is a drawback, I know). But the price difference seems backwards. A completely separate issue is, the way I see it, motorized varifocal is a waste unless the camera is PZT.