I have a DK 45 and compared it to the Mahindra 4110 prior to purchase. It really came down to I could get 5 more HP for only a few hundred dollars (the DK 40 was 100 dollars less than the 4110) and I really like the Kioti dealer more than the Mahindra dealer. However, if there was no Kioti dealer, I would have definately gone Mahindra.
I don't know too much about the 4500 series, because when I bought my tractor a year ago they were only offered in 2wd and I was determined to have a 4wd (I was spoiled by my Yanmar and Belarus 4x4s). I would agree with the previous comment that the 4500 is more of a utility tractor than either the 4110 and DK 45, but I know there a couple of folks that square bale with a DK 45. The fella that bales our hay has used an old IH "M" Farmall, which I think is in the 40 HP range, so HP wise, I think any of the tractors could handle. I don't think you can go wrong with either the Kioti or Mahindra. Go with the one that is cheaper and you feel more comfortable with. Good luck.