A bobbin sander is best for curves and shaped work, on a straight panel edge you risk little divots where the bobbin sander has stayed in contact with one part of the edge for a bit too long.
A flat belt sander is best for production work, where the sander belt is horizontal with the belt visible and there's a big, flat table in front of it to support the workpiece at exactly 90 degrees to the belt. That way you preserve crispness on the arrises and straightness on the edge. You can rig up a hand held belt sander to work in this fashion, and that's often a better solution than a smaller floor standing belt sander because then you can use the full width of your bench as the supporting table for the workpiece.
For a hand held tool and lower volumes the smallest orbital sander is best (less tendency to tip sideways), but make sure the backing pad is really hard (the standard pads never are, a quality tool will always offer a selection of different backing pads) as this helps prevent dubbing over the arrises.
I've got a Festool rotex 150mm that I use with the hard pad coupled with their Granat sanding discs for mdf edges. I literally have sanded 1000 metres of edges down to a 240 finish prior to spraying and can't fault it. It's heavier than the mirka type sanders but the speed of sanding makes up for that.