Which one is better performer on wrangling big data, R or Python?
I think this may help you:
Is the R language suitable for Big Data

I think it really depends on what you are comfortable with and what your objectives are.  In Python, I can execute SQL queries directly into Pandas data frames.  From there, data cleaning and visualizing (I like seaborn) is fairly straightforward.  I can easily perform matrix manipulations using Numpy, and the sklearn is a well documented ML package.

That being said, I still like R and there are definitely times when I will use R.  Learn both!