I also have the Bernina 440 and it's my favourite of any machine I have ever used. I can use any kind of thread and it sews perfectly. Even using monofilament in the top and the bobbin doesn't cause a bit of trouble. I've never used a machine with accu-feed so can't comment on that, but I have never had trouble piecing with the #57 foot. It doesn't have a thread cutter, which doesn't bother me but might be a problem for you. I have several bobbin cases and can adjust the spares easily for things like bobbin work. I have never liked drop in bobbins though so it's not surprising I'm happier with the front-load. The stitch plate just pops off without tools for easy cleaning and the feet are equally simple to change. I'd also miss the free arm, which I think only the new Horizon has. I do use both the stitch regulator and the embroidery module, so they were extra reasons I first decided on my Bernina.
Bernina's biggest negative in my view is the price.