Those two images have the same content, but are generated for different NAND flash configurations.
The number after the timestamp refers to the "erase block size" of your flash memory and that does not have anything to do with your partition sizes.
You can verify your module's erase block size by running "nand info" at the u-boot's prompt.
CCARDIMX28 # nand info
Device 0: nand0, sector size 128 KiB
So for your 256MB NAND flash memory you should be using the "dey-image-minimal-ccardimx28js-20171102190445.128.rootfs.ubifs" image.