Now I'm going to have to do some testing between my vertical and drop-in bobbin machines...I've only done FMQ on my Janome 6600 which is drop-in and it never occurred to me that the bobbin style would make a difference. MOST of my machines are drop-in, but I have a couple verticals. Of course the 6600 is really the only one with a big throat...
(Sorry, more hijacking!)
I've never sewn on a 400-series, but I recently took my Rocketeer with me on a little vacation and I am REALLY in love with that machine now. It sews SO nice. I'm sure I'll get ahold of a 400-series some day but so far one hasn't fallen into my hands.