Horses for courses – if you want fast, go tunnel – you can usually be through and on your way on the tunnel in the time it takes to get on the ferry, but the ferry offers more of a rest for the driver, change to eat and whatnot, there’s a small toilet on the tunne, they’d like you to stay in your car really.
As for the migrants – we spent 4 hours in a queue last summer – some issue with a ferry and Obama had just arrived in the UK for the NATO thing so the port was a defcon 1. Yes there’s hundreds, if no thousands of them milling about and occasionally the police chase them about keystone copslike but I never felt intimidated, they annoyed the truckers though. It’s really all very secure – I don’t believe they ever forced their way into anyone’s car – hearsay and paranoia I’d say – you’ve got two layers of security to pass once you get past where they are – no way the guards are going to not notice the 20 year old Somali lad sat quietly between the kids in the back seat, or hanging from the exhaust and they know that – better to try one of the thousands of trucks about.