Should I use Chapel or Julia for my next project?

Julia and Chapel are both newish languages aimed at productitive scientific computing, with parallel computing capabilities baked in from the start. If you are starting a new scientific computing project and are willing to try something new, which should you choose? What are their strengths and weaknesses, and how do they compare? Here we walk through a comparison, focusing on distributed-memory parallelism of the sort one would want for HPC-style simulation. Both have strengths in largely disjoint areas. If you want matlib-like interactivity and plotting, and need only master-worker parallelism, Julia is the clear winner; if you want MPI OpenMPI type scability on rectangular distributed arrays (dense or sparse), Chapel wins handily.