The CK30 has a PTO HP rating of 24HP, the DK35 is 28.3, not a lot, but a more powerful PTO, which would translate to a little more power to an implement.
The CK30 3pt lift capacity is 1754#, DK35 is 2425#.
With the DK35, you get position control, draft control and mixed. With the CK30 you only get position control.
The DK35 only comes in synchronized shuttle gear transmission, the CK30 in Hst/synchro shuttle.
As far as pulling etc. there isn't a great deal of difference, but if you need a little more PTO HP, and more lift capacity, the DK would be your best choice. Of course, if you want HST, you'll have to go CK30 as it's the largest thing Kioti offers with HST at this time.
You may prefer on style over the other as well with the CK having a sloped hood and curved arm loader, the DK having squared hood and dog leg loader arms. A little better visibility on the CK. Either will probably do most anything you'd need to do, not knowing exactly what it is you will be doing.
Go sit on them, and get a feel for how they fit you. It's a toss up in many ways. John