I own a Janome, 8900, and love it. I purchased mine off Craigslist and chose to search for a Janome as there is a dealer about 45 minutes from where I live. The piece of advice I have to offer is this, consider picking the machine that has a dealer near you. If you have issues with a machine, relying on the dealer to fix it and service it is important.
The 9400 is the next step up from my machine, it has all the bells and whistles, there is also an expansion kit available to purchase that adds even more features to the machine. I don't know anything about Bernina machines as I have never sewn on one but as I've read on here multiple times, I have observed several of us quilters have our preferred brand of machine, so I'm sure someone will offer advice on the 770 for you to consider. Good luck on your decision.