DN - Takes Skill as previously mentioned, you need to know the rulings, no timelimit, players are much better, some can be annoying, but overall the quality in terms of players is much higher once you get to 1200+ , no download required, in case of misclick ( put your monster in def when it was meant in atk) you can put it correctly.
ygopro or devpro - Most of players are noobs, can be automatic but rulings arent always correct, timelimit sucks, you need time to think and make your plays, having to download while we have a non requirable version is dumb, and the chat quality is not that great. Only thing i like is the tag duel mode, that's all ._.
Overall as you could have notest i prefer DN.
DN >>>>>>>>>>>>>>>>>>>>>>>>> ygopro but this is me, of course.