I have the Brother PE770, besides a Bernina QE440, a older Singer Serger and an Innova Longarm with AutoPilot.
I agree with Nanamoms, embroidery field size is the most important aspect. Generally, the larger the hoop your machine can accommodate, the better. I've had lots of fun with my PE770 and have done several T-shirts, bibs and smaller quilts. The quality of the stitch, especially on the quilts, using continuous line embroidery designs, is beautiful. That's what actually convinced me to buy a longarm with robotics.
Like Nanamoms, I'm also self-taught. I bought myself a good general machine embroidery book and read and followed the instructions since I was new to embroidery. Because the machine only does embroidery, it's very straightforward and easy to use. Biggest issues I've had are with brand of thread. Mine seems to prefer Gutterman. I made the mistake of ordering some bulk "embroidery" thread on e-Bay, but no matter how much I adjusted tension, changed speed, stabilizer brand, etc. it was just shredding and breaking. Had to fish shredded thread ends out of the tension disks several times, until I learned which thread my machine liked. But the machine kept running no problem, even with all the tinkering I did. I've bought several of the Brother embroidery design cards but these seem to be going by the wayside as the new machines connect directly to your PC. I also transfer designs to my PE770 using a USB stick.
Bottom line: I've found my Brother PE770 to be very dependable and a good value for the money.
Good luck with your decision.