Bison is now upgraded from arm5 to arm7, following many other engines. By definition it should play stronger than the arm5 binary.
Meanwhile, don't be surprised by the variety of the engine ID's shown here and there. The original version number is 9.11 (probably for November,2009) while the GUI's will show 15.12, the year and the month the binary was compiled. Don't take it as the real version number.
Anyway, it's an old engine abandoned long ago and we know it's 9.11, regardless of what will be shown.
Don't forget to install Parameters.txt as well the same way you install the engine. The name MUST BE Parameters.txt and NOT parameters.txt!
Download Bison 9.11 for arm7: HERE