I just want to put in my 2 cents for this particular Brother sewing machine. I have had mine for a few years, and I have made a couple of duffel bags, a ski bag (pattern from quest outfitters), curtains, clothing alterations, and I am in the process of making a MYOG pack. I have sewn through 1000D cordura, XPAC, and various types of webbing.
I have also sewn with my mom's Singer, my Aunt's Kenmore from the 1970s and a slightly more modern Kenmore and I would take this Brother over all of them.
It has a fantastic user interface – it is extremely fast and easy to thread, you don't have to raise the bobbin thread (saves time), switching needles/presser feet is a breeze. The needle always stops in the down position when you stop sewing, which makes it easier to be exact and execute pivots. It also has a setting which limits the max sewing speed, which was really useful when I was getting used to it.
It sews through a lot of tough fabric easily. I discovered its limit when I tried to sew through 5 layers of XPAC and 2 layers of webbing, however, I was able to hand crank the machine through that section. When I hem jeans, it smoothly rides over the thick vertical seam without missing a beat.
I find the feed dogs to feed very well. At some point I tried sewing lycra binding with my mom's Singer, and the lycra kept getting sucked into the feed dogs, but the same lycra binding was easy to sew with the Brother. I rarely have tangles with the bobbin thread.
In short, I instantly became a better "sewer" when I got this machine.
As for thread, I have only used the Guterman from Joanne's. I have tried the thicker Guterman from Joanne's and it worked, but I felt like the tension was off and I couldn't fix it, so I've stuck with the standard thickness.