The CS runs a "unique" version of Android OS, not the same as you have on a Android phone. Thus the app and OS have to be updated by DJI, and they are not current. DJI makes a point of this in the FAQ on the CS. You can expect updates to the CS app and OS about 2 weeks after a update to the other android OS for phones or tablets. This is also true of the P4 Pro Plus as even thought the monitor attached is not a CS, it's still running a unique version of Android OS.
I have the CS high bright 7.5, net I feel it's not stable enough to use on a P4 Pro as I have had too many app disconnects. NOTE, these are app disconnections not RC disconnections. However if you are flying out far, your only option is RTH and hope it works OK. There are also issues with video pixelation during flight, but with the latest firmware updates to the CS these appear less often, mainly on pans. With the app disconnections, you can also have video freezes, which are just as bad as you again have lost video for flight.
On the Mavic, where I still use the CS, I have not seen these issues, besides pixelation at times during the feed.
Brightness, the High bright is 1000 nit quite bright. From what I have read the iPad pro 10.5 inch is around 500 to 600 nit. I am not sure what the brightness of the 9.7 iPad is, however I don't believe it's as bright as the 10.5 or 12" Pros now on the market.
So differences on paper are not that much, however the CS just seems to handle the direct light much better than a Apple retina screen. The retina screens are basically mirror in the daylight, so you have to have a hood, at least I do. The ultra bright CS is 2000 nit, and there is a difference between the 1000 nit and 2000 nit, but not as much as I thought there would be. Also the monitors have a glossy screen so you will have reflections to contend with depending on the angle of the monitor to the light. There were a lot of problems with early versions of the CS Ultra bright, mainly screen burn outs. DJI pulled them for about a month and have started shipping again, so they may have fixed that. However at 1K, with no application use, it's a very expensive alternative.
There are some issues where the CS gets will over heat and shut down on a hot day, but this can just as easily happen with an iPad.
The design and features of the CS are top end. Nice size and package. However DJI can't seem to make the actual hardware stable, at least for the Phantom series. The touch screen has nice tactile feedback and makes a clear sound when something has been selected. DJI has a great mount for the CS on the Phantom controller also. Battery life on the CS battery is long and should last all day, make sure you don't turn on the wifi on the CS, as if you do the battery life will drop even if you are not connected.
One other note, the CS does not come with any charger, so you need to use your Phantom style charging plug.
Paul C