I make my own seam guides from moleskin. Even better is the Dritz Adhesive Guide Refills (don't use their red ruler as it will make the seam too large). I'm also going to try the 3M Command large mounting strips. All of these provide a physical guide against which you can butt your seams. Makes my sewing much faster and more accurate than if I just eyeballed using a 1/4" foot.
I can't be sure from the Amazon descriptions, but I think the Janome may not have adjustable stitch length and stitch width capability. It only mentions built-in stitches. In my opinion, you *really* want to have variable stitch length and stitch width alter on for machine applique options (and it also creates more variations in decorative stitch options, as you can alter the look of a single decorative stitch by varying stitch length and width).
My Bernina has the straight stitch plate, but I ***rarely*** use it. Broke too many needles with it from mindlessly changing to a zigzag stitch without remembering to change the plate. Not all machines draw fabric into the zigzag hole, plus it's fairly simple to avoid this by using leaders and enders (small pieces of scrap fabric used to start and end stitching lines, sometimes used to create scrappy quilts too).
Personally, I would opt for the Brother. You can add in accessories slowly over time, as you need them. Generic feet are inexpensive and usually do a good job. The one exception might be a walking foot, as sometimes these work better if you buy the walking foot made expressly for your machine. But that's not something you need right away.