There are 96 reviews of the Brother on Amazon:
http://www.amazon.com/Brother-PQ1500...dp/B003C29EL4/
There are 13 reviews of the Juki on Amazon:
http://www.amazon.com/TL-2010Q-Locks...dp/B00AAZU1KE/
I believe the Juki is a much newer machine.
Also check out reviews at
http://www.patternreview.com . You need to create a free login to access all of the reviews. Select "sergers/sm" and put in the brand name, then scan the reviews for the models.
In general, I give more weight to people who have used a machine for more than a week or two, as they are more likely to have a balanced view.
In the past I have seen a few comments about tension issues with the Brother, more so than with the Juki.