Sunda accent can be so though. Even if you are grow in Sunda, and able to fluently speak sunda, still you unable to speak Sunda naturally, and the language are bit complicated. While Javaness, the slang language which is commonly use or the ngoko, are very easy to be understand and master, because it come up with as ecletic with other Indonesian language. But if you are talking about the Kromo or Kromo Inggil which is the finest form of javanese language, it is like entering an entirely different words and learning all from the begining, but it's not practical because peoples aren't use that language in daily conversation except if you living in keraton (javanese palace) ;p so judging by ngoko javanese, sundanese is tougher to master. But judging by kromo or kromo inggil, even many of the native javanese can't speak those language.
it is :)