Sjaak II finally came to 1.0 after many betas. We used to have beta5 compiled by Jim Ablett. Now, Androiders can use the same latest version as Windows.
I've tried to import Sjaak to Chess for Android using UCI. It loaded fine but i need test games to confirm full compatibility for tournaments later on. Glad to see Sjaak providing UCI too.
In any case, and by default, whenever we have an engine which claims UCI and Xboard/Winboard compatibility, we must absolutely try UCI first.
One main strict reason is: Hash size, number of threads and tablebases can only be configured with UCI protocol but only default settings can be used with XB. This means that on Android, all XB engines lose more strength than UCI. Take UCI when available as a rule.
Also, i must mention that the beautiful alternative GUI Droidfish can NOT use XB engines at all.
Download Sjaak: HERE