Dutch will be easy and difficult at the same time. The similarities will make easier to learn it, but at the same time will make it difficult, because of "false friends", different genera, etc. The problem I had with German wasn't really the akkusativ, dativ, genetiv; tenses, etc. I had more difficulties with vocabulary, preposition,...
Nominative, ablative, ... are called cases (grammatical cases). Those cases are really different than the German ones, in German you only change the article and you put sometimes a -s or -n behind a word. In most other languages with cases, the whole semantic structure of the word changes. And Hungarian has about 16? Like Finnish or even more.
The difficult thing about Hungarian, Turkish & all non-Indo European languages is that there are no semantic similarities and grammar structure is totally different (a lot more cases, different moods, time aspects are different, etc.).
Example: we say: my book, mein buch, mon livre, mijn boek,... [possesive adjectif+noun] if you want to express this with the meaning in Hebrew, you say: the book of me.
I don't think 'cases' should influence your choice. At first, they can be hard to learn, but at the end, it easier to analyse/translate a text with cases than without (that's my opinion). You should go for a language AND culture, you really like. If you don't like the sound of it, don't choose it. Every language is difficult to learn, and it's different to each one of us.
I'm gonna study a new language too next year. I'm probably going for Hebrew (or maybe Hindi
)! Anyways good luck!