Какая файловая система наиболее предпочтительна для SSD дисков?

ext4, потому что поддерживает команду TRIM (опция монтирования discard).

At present, ext4 is the only fully-supported file system that supports discard. To enable discard commands on a device, use the mount option discard. For example, to mount /dev/sda2 to /mnt with discard enabled, run:
mount -t ext4 -o discard /dev/sda2 /mnt
By default, ext4 does not issue the discard command. This is mostly to avoid problems on devices which may not properly implement the discard command. The Linux swap code will issue discard commands to discard-enabled devices, and there is no option to control this behavior.

(с) RHEL 6 Storage Guide