The Pro does indeed have an IPS display. .27 lbs is a negligible weight difference.
I personally would rather have a superior screen vs the T2 chip and a v3 keyboard.
I agree, but... you can configure the Air with 16GB Ram and 256GB drive for the same price as the nTB Pro with 8GB 256GB. That being said, the 300nit dismay is hard to look past...
I'd have to use one for a few days in my environment and not in the bright Apple store. I guess on the flip side of things my work HP Elitebook x360 1030 G2 only has 250nits, and many top Lenovo laptops, including the X1 line have below 300 nits. Adding to this I never actually had a problem with brightness on my own Air and it was around the 300nit mark too.
I keep my brightness between 50% - 65% on both my nTB and 12", so while it would be hard to look past that low nit screen, the thought of 16GB/256 for the same price as the nTB would be enticing.
If the Air was someones primary laptop, and didn't care to compare side by side, I doubt many would notice the low nit, and it'd be a perfectly fine display for them. I think the people who care the most are on this forum