For me I would go with IGBT's being they are robustly built, easy to control with a dedicated driver IC and little else, plus they generaly have high voltage ratings and good current handling abilities in a small package and are rather cheap to buy.
For basic ratings I would suggest using something with a 2x volt rating over your peak rail voltages and at least 4x your estimated peak amps you plan on switching so any that are rated at 600 V or higher and 30+ amps should be good enough.
As far as frequency goes 50 Hz is pretty low far as IGBT's are concerned so that wont be a problem with any model you chose.