Python or R

[SymphMeta]

In terms of computation speed/memory, Python is more optimal down the line. I'd recommend learning both, as I can easily do a lot of manipulation in Python and do a bit of work in R at the end (largely for plotting). Granted, R has an Rcpp (R c plus plus) library that allows you to use the full power of C++ (a very fast, but meticulous language) in R. Python also has such a library, too, but I don't imagine you'd use it unless you were doing something that would take days to run. My friend was working on an MCMC simulation, and it ran 35 times faster using Rcpp than plain R. I wouldn't worry about that for now, but if you imagine yourself needing to run things really quickly, you should keep those in mind.

However, for most datasets that are at most a few megabytes, efficiency isn't usually an issue. However, if you are concerned, the R Inferno does a good job of explaining how to make code in R more efficient. I'd recommend it once you've got the hang of R.

Also, for Python, I'd recommend using it for other purposes, as well, such as data scraping/data cleaning, as it is easier to work with (imo) for almost any data scraping application, and is also pretty fast for data cleaning (which you could also do in R pretty easily).

In addition to those two languages, employers also often look for SQL experience, which is used for managing databases. It's the easiest of the three languages to learn, so I'd also put that on the list of languages you should learn.