neXus employs the use of a reflection system, which essentially is an anti-ban system 10 fold times better than RSBuddies; RSBuddy utilizes the injection system.
As such, neXus bots are exponentially harder to code, however, this makes them more resistant being detected. Consequently, the available selection of bots for neXus is exclusive.
RSBuddy on the other hand has an enormous script repository available for you. There are honestly 1000's of scripts, hundreds of them not only working, but near flawless.
While RSBuddies anti-ban system, injection is far more detectable than NeXuS's reflection, the ban rate is still extremely small, well less than 1%.