Low light focus speed and picture quality over the years

I did a little informal test tonight on my 3 Pentax cameras. ist-ds, k-10d and new k-01. In a dimly lit incandescent  room the k-01 focused faster followed by the k-10d then the ds. In a fairly bright fluorescent lit room the k-01 was still faster by a hair and the k-1od and ds were about the same. Picture quality ratings were k-01, k-10d and lastly ds. All tests and photos were done at iso 1600 at f1.7 using my f 50 1.7. I was a little disappointed at the quality of the old ds in dim light. I always thought it did fairly well at high iso.