OK, just tested the Pocket RAR v3.71 on my GloFiish X650. I'm very happy because it's free, official and works fine for me. Compared to the big brother from PC this one has some limitations, including:
+ Supports only RAR and ZIP, both compression and decompression though
+ Has no additional compression settings - only archive format, compression level, Solid-mode and volume size.
Overall, compression performance is close to the PC version, I think due to some memory limitations Pocket RAR uses the main LZ77 more frequently than it's bigger brother, also in many cases it still uses PPMd, but looks like with smaller model size. So, the results:

world95.txt - 636,904 bytes
fp.log - 806,306 bytes
acrord32.exe - 1,412,453 bytes
rafale.bmp - 805,978 bytes

ENWIK8 - 27,933,019 bytes

calgary.tar - 804,610 bytes