The clock which doesn't work shows correct time twice a day. But a clock losing 1 minute a day doesn't show the correct time at all. 
From this point of view, a incorrect clock is better, but neither of them are of any use.
1 5 1
The second one which doesn't work because it shows the correct time two times or twice a day..!! This is the answer for this riddle.Hope it helps and pls mark as the best answer. :-)