I have the 7700 and I really like it. The stitch quality is good and there are plenty of stitches other than straight stitches on the machine. I like the throat size and the lighting. It has a built in walking foot that is great, but when the machine is new, it's a little cumbersome to put on and off. It comes with a nice size extension table. A note, when you take your throat plate off to do a thorough cleaning, be careful about how you put it back on. There is a clip on the throat plate that has to fit properly. But the dealer can show you better than I can explain. All in all, I love the machine and am not sorry I bought it. It's a work horse.
About a month after I got my machine, I had to take it into the dealer because the mother board went out. No rhyme or reason, it just failed. But the dealer and Janome took care of everything and it's been perfect ever since.
I am going to suggest that you visit a Brother dealer and a Janome dealer to test drive both machines extensively. And if you do this, take fabrics from your stash to run samples on. That stiff fabric they use to do the demos make every machine's stitches look good. So take your own stuff and then you will have a good comparison of what each machine does.