The two Bernina sergers I owned were indeed fantastic machines. My first was over 30 years ago and was a Bernina 2-3-4, I believe. The next one was a 2000dce. They could sew anything.
I just looked at the Juki 654 because it gets really good ratings but the knobs in the front remind me of that first Bernina serger which, while a great sewer, was a real nuisance to thread. The 734 is only £20 more.
Yes, I soon thought of the way around serving cuffs. You're right; the free arm is not necessary.
The only thing is the dealer where I bought my Bernina doesn't sell Juki. (No wonder he recommended Babylock but no way am I paying that price.) Good news is that there is a Juki dealer about an hour away. That's not bad. Touch wood, I have never had to take a serger to a dealer and hopefully won't in the future except perhaps for servicing