T54IR is a sensitive color camera which can work at night in color mode - and comparison is highly recommended - with the same external white street lighting (no onboard white light usage on white light models)...
Especially that T54IR is a benchmark on this forum...
Everyone knows this model and know what is performance at night...
5x59-IL (Smart Dual Light) is a replacement for T54IR in Dahua portfolio...
After reading your notes on the specs, and then going and looking at them myself, like you I find it odd...
From pure spec, I see no reason to buy the IL vs the PRO? IL simply loses a few features, speaker, IVS for dummies, but has much worse FStops
The Pro I fear will be much like the 3449 pro in that it will pickup light better, but with the digital noise as a tradeoff.
The IL with the much worse Fstops, equal to (replacement for) the old 5442-S3 is likely to have the better IQ but at the expense of not being as light sensitive.
Seems we're back where we started? 5442S3 vs 3449 Pro?
IF the noise is still present on the PRO and my guess is right that the IL has the image quality of the current 5442-S3, but ALSO has the white LED's and Smart Illumination, I might be tempted to stay with it and not mess with the PRO. I mean there's very little feature difference....
Seems it will come down to image quality, unless Dahua puts a crazy price premium on the PRO