This article doesn't mention which compression algorithm was used with UBIFS.
Compression algorithm has a large effect on the speed. For example LZO is very fast at uncompressing and compression is also fast, although that depends on what LZO compression level is used.
Whereas ZLIB compression is significantly slower for both, but provides better compression results.
Which one to choose depends on:
* What kind of data is being stored
* Flash write and read speeds
* Algorithm compression and uncompression speed compared to those (which depends on CPU speed)
Article mentions using high speed PC, so for it algorithm with best compression ratio would probably be best. On Nokia's Maemo devices low level LZO compression was used at run-time, but pre-made root file systems were compressed using highest LZO compression level (this explains why apt-get upgrade could leave less disk space although binaries were same size).
As to data types, non-compressable data like music, videos etc is typically user data and it can even be on a separate partition / storage media (on Maemo devices, SD card) with different file system, than the root file system which contains the binary data, logs etc.