1) how common are comms failures? I mean actual failures not just the muppet on board has dialed the volume down ( yes I've done it!), given that I have two radios on board, should a backup hand held be a priority?
The only radio failure I have had in 30 years of flying was when my alternator packed up over the north sea at the start of a long trip to Hungary in a single seat, single engine LAA aircraft. I used the handheld to allow me to switch off the aircraft radio to reduce drain on the aircraft battery.
Having had both ICOM and Yaesu, I would say the Yaesu is much better value for money as it includes all the extras, desk charger, AA battery pack, car charger, headset adapter etc etc.
Performance wise I couldn't tell the difference.