I consulted my Singer repairman when I was looking at both. He highly recommended the Juki over the Brother because it had metal parts inside vs. plastic on the Brother. He was not a Juki dealer...just someone who was familiar with both. He said he rarely saw a Juki in for repairs and that sometimes it was difficult or takes too long for Brother parts. I've had the Juki for 2.5 years and love it! It's been perfect right from the box. It's not fussy about thread and I never have to mess with the tension. It cost more than the Brother, but I have zero regrets and would buy another in a heartbeat if anything ever happened to this one.
That said, there are many with the Brothers that are quite happy with them too.