I’ve done both, they have their advantages – tunnel is indisputably faster, there’s less waiting to get on, less faf, a much quicker trip and much quicker disembarkment – but there’s also no rest for the driver really – you can get out of your car, but it’s not encouraged and there’s nothing to do anyway, bar the odd toilet.
The ferry is a decent rest for me and means only one stop between Calis and the Alps.
All that said, given all the issues at the moment is take the Ferry to Dunkirk, I’m told it’s much quieter. I’m not worried about asilum seekers, but it took us 4 hours to get into the port last year.