It's less about the difficulty, but the more about the struggling with the piece itsself, looking at the score I think you should not come across many problems...try to have a read of the first measures of the adagio and of some of the other you may see that there's a changing of tempo 2/4, 3/4 and so on and then you'll decide, Bach it's a big deal you have to struggle with whathever you choose of his works... I studied the whole first partita in B flat and I have to say that I struggled much more with the courante than with the prelude F minor n.12 WTC II