Having just completed a rapid trip at short notice to Belfast via Stena routes, on ships analogous to some well-known to BF fans, I thought I'd record some thoughts on the comparative offerings.
Outward was overnight from Birkenhead on Stena Lagan, a Visentini. I've never fully appreciated the significance of comments on the ramp on these vessels until now. Golly, it's steep and narrow! Once on board, we found the bar and enjoyed a drink and a snack, then pausing in the coffee bar to collect a couple of hot chocolates to take to our cabin. I have to say that the choice and quality of the food was excellent, even if it was a tad pricey. Although the half price refills of hot drinks was a nice touch. Our outside cabin was very comfortable, a little bigger than the usual BF offering, but the real difference was in the mattress. Wow, that bed was comfortable and we had our best night's sleep on board a ferry for a long time.
The return crossing was to Cairnryan on a superfast. However, this one still has its wings and the interior layout is completely different from Cap Finistere, reflecting the completely different pattern of usage. Loading and unloading was on 2 levels and both bow and stern doors were used, so no interior ramp and no whirligig driving round in circles. The Hygga lounge was very comfortable and convenient for the self-service cafeteria (where again the choice and quality of the food was excellent). The only criticism I have is the television would have been better with the sound muted.
All throughout the staff were friendly and helpful and I couldn't fault the customer service. The worst parts of the journey were getting to Birkenhead (overturned vehicle on the motorway and M6 roadworks) and the long drive from Cairnryan to Dorset with no heater in the car!