Replacing Macbook Pro SSD with Macbook Air SSD Currently I have a Macbook Pro (mid 2014) with 120GB ssd. I am planning to buy a Macbook Air (say, early 2015) with 250GB ssd and swap these drives between laptops. I know they are both PCI based, but that doesn't mean much
as the protocol could be SATA/NVM/Proprietary.

My concerns are:
1. Will it work?
2. Should I expect significant performance differences between these drives?

I checked compatible drives for both laptops on ifixit:
https://www.ifixit.com/Store/Parts/MacBook-Air-11-Inch-and-13-Inch-Mid-2013-to-Early-2015-and-MacBook-Pro-Retina-13-Inch-and-15-Inch-2015-SSD/IF188-105-5 Air

https://www.ifixit.com/Store/Parts/MacBook-Pro-13-Inch-and-15-Inch-Retina-Late-2013-Mid-2014-SSD/IF123-026 Pro

I see that Air's SSD is compatible with Air models from 2013 to 2015, but with Pro models only of 2015 -- that seems weird and I expect that it's just a misleading description. Does anyone have such (successful or not) experience?
I agree with Matthew.
MBA early 2015 connector PCLE 8GT/s
MBP mid 2014 connector PCLE 5GT/s.
I suppose it can be done, but I would not do it at all.
You have to reinstall everything including the EFi and RecoveryPartitions, otherwise it will not work at all.