The default FS is more tuned to small files and the usual day-to-day work.
(JFS and XFS are the usual recommendations for handling big files, but do benchmark.)
just what android needs. a new filesystem for those cheap flash storage inside the phones and tablets, some of them aren't even extendable. SSD is a very different case since the controller chip itself have a mechanism to *minimize* wear and tear, thus needing the filesystem to only support the features such as TRIM to work properly, that is why there's no need to have a proper filesystem made for them.