The IMX 291 based rear camera are the most sensitive one, but IMHO it dosent matter as rear cameras only work at night with a little ambient light around, and even then it is marginal in regard to resolving small details at speed.
I have no problems with the IMX 323 based camera of my DC model, i see no reason for upgrading that even if i could, but for the front camera i would prefer the IMX 291 sensor anytime.
The IMX 291 are more easy on the eye, meaning you can see more in the footage, but if you pause and look at the footage or go frame by frame, you will notice the more you can see, well it is a blur that your eyes compensate for when you view it in real time.
I think the IMX 291 use pretty much the same settings a IMX 323 would under the same conditions in low light, so this mean 1/30 second exposure timing and a high ISO.
If only the IMX 291 was substantial more light sensitive and so could use faster exposure timings, then it would be a whole other matter, but sadly we don't have that good sensors yet.