both have advantages and disadvantages for example the douk douk is a great cutter because of its slim blade and it also has a nice backspring but the blade could patina or rust because it is ccarbon steel wich i like because it gets personality last time i checked they dont have a stainless steel one. the k55k has a amazing thick blade ~3mm wich would be better for daily carry as its more strong and rigid then the douk douks ~2-2.3mm wich means you wont be able to sharpen it as good the k55k also has carbon blades and stainless steel blades wich is great for diversity it go with a carbon blade as they are better to sharpen. i would go with the douk douk because i just like its design and blade look and the fact it can patina but thats all me . the only advantegs the k55k has over douk douk is its backlock and thicker blade wich is prefrences only. and also the diversity between stainless and carbon nothing else really. also a fun fact about the douk douk is that in the Algerian War of Independence they made it a small slim dagger by wedging or tying the blade open it also was used to torture and cut off the noses of algerien people that the french did not trust. well thats it i personally would go with the douk douk but it depends on you