If they had to ditch they were stuffed.
Weather was solid force 6 from the SW at the Channel Light Vessel at the time, varying between 23&30knots if I remember correctly. Dull and overcast/cloudy in Guernsey during the afternoon. Later in the evening (10pm?) I noticed the weather deteriorate as a front came through (gusty, sleet/hail/rain). Sea state at the CLV was 2m waves every 6-7 seconds - a very heavy 'chop' as opposed to a swell. Would have been classed as 'rather rough or rough' I suspect. It's 'spring tides' with a decent run of current in the area.
When CIAS first started searching at 9pm they had over 10 miles visibility, although I don't know what the cloud base was. It got worse and they had to give up as the cloudbase dropped too low. This is from pilots who regularly fly below clifftop height (100mASL).
Even if they managed to 'land' nicely on the water they'd have been swamped within a minute and almost certainly sunk. Alderney Lifeboat have some footage from yesterday's search on their facebook page when the weather was nicer than disappearance night. Proper horrible. I've fished up round that way a fair bit in nice weather, on that night it would have been apocalyptic to be bobbing around in the sea. If by some freak of luck they managed to get out alive and get to the Casquets or other reefs off Alderney they'd have been smashed up in the breakers trying to get out the water. I'm amazed at the amount of effort put into the search, had it been a fishing boat with two crew that disappeared they'd have given up by lunchtime the day after.