I haven't used PyMTL but have used MyHDL, years ago. (I'm glad for aseipp's comments because that proprietary mess is exactly why I haven't bothered keeping up with FPGA development, though IceStorm has gotten me interested...) Glancing at PyMTL it seems they're comparable -- neither require that much code (https://github.com/jandecaluwe/myhdl). I'd say without digging deeper MyHDL is older, stabler, better documented, and has been used for real world projects including ASICs. PyMTL might allow for more sophisticated modeling. I'd be concerned about PyMTL's future after the students working on it graduate, whereas MyHDL is Jan's baby.

Found http://ucsbarchlab.github.io/PyRTL/ which has a good overview of these sorts of projects.

Thanks!