I've worked both. MK is my home location, but DAK is my "home away from home" since I pick up there all the time. Harambe/Africa and Everest/Asia are my two favorite places to work on property hands-down. Both have advantages and disadvantages.
Both parks take the longest to get to from the CP housing. Parking is MUCH easier at DAK, it's right by the front gate and you can walk right in through the front. Compare that to parking at MK's Westclock and taking the bus to the park, adding 15 minutes or so to any commute. I love parking at DAK.
MK has the utilidors which is both nice and a pain in the butt; lots of stairs but everything backstage is indoors and air-conditioned (NOTHING backstage at DAK is air-conditioned).
You're outside a lot more in general at DAK, which may not necessarily a bad thing. Might not be great if you're not a fan of heat, but the environment is IMO more interesting because you'll find yourself helping guests find animals or answering questions about them. Working outside and being surrounded by the park environment, characters, etc is sometimes preferable to being stuffed in a little store all day.
MK has more entertainment, fireworks, more parades, characters walking around, etc. DAK you get one parade and that's it.
DAK has much more interesting merchandise in all of its locations, African sculptures and masks and Asian clothing, vs. MK's typical Disney stuff, Mickey plush and WDW tees and all that stuff.
DAK makes you stock a lot, the most out of any park. Some people don't mind stock but I hate it. You'll be doing stock just as often as you'll be doing registers. DAK is also the only park I've heard which makes CPs do HOH or "Heart of House," which is when you go in before park opening and organize/set up merchandise for the day. Sometimes this'll be at 5 or 6am. MK has what is practically a devoted HOH team so CPs generally don't have to do it.
DAK gives 15 minute breaks, MK gives 30. I miss the extra time every time I work at DAK. The DAK breakrooms are generally a lot newer/nicer (unless you work on Main Street... they win for best breakrooms at WDW).
Obviously hours at DAK are a lot better and more consistent. I'm at MK usually til after midnight every night, DAK you'll rarely be there past 9, freeing you up for nighttime activities (and this is the CP so there are many). Conversely you'll have to get used to getting up early.
Hope this helps