So far I've found three comparos between the One and the latest MkV Golf. In two of the tests, the Golf was rated as the winner, although
they said that BMW was more fun to drive and is dynamically in
another level. But (unsurprisingly) the One lost so much ground in interior space and price, it couldn't beat the Golf with handling alone.
Since both cars have 150bhp and weight the same 3000lb, standing start acceleration times were almost equal (0-60 in high 8s), but the One's overly tall gearing hurt its in-gear times where it couldn't get even near the Golfs times.

Btw: The "Sportline" version of Golf has e.g. sports seats, 17in alloys and a sports suspension. But don't confuse it with the new 200bhp turbocharged GTI.