JeOS filesystem

Hi all, I have a question on JeOS images being built for ARM boards. I suppose that we agree that most target SBCs use microSD cards to store and run the OS. There are exceptions though. Currently, half of JeOS images are supplied with ext4 and the other half - btrfs. And frankly speaking, I cannot figure out the rule why some specific board receives JeOS with ext4 instead of btrfs or vice-versa. I suppose this was related somehow to btrfs support in u-boot, right? Another consideration. Does anybody know any research on what FS is the most friendly to SD cards? -- With best regards, Matwey V. Kornilov