I have, or had, both machines. I love both, the Brother CS600i has more stitches, more flexibility, The Janome Jems are wonderful too. The Jem Gold has preset stitches so you can't change width or length but is very strong and sturdy. There is also a Jem 720 & 760, they re computerized, more expensive and have more flexibility but I think are discontinued.
You can't go wrong with any of them, I gave the Brother to our oldest granddaughter, and Jem Gold's to younger grandchrildren-great machines for children wanting to sew.