Well, I don't have any comparison pics right now, but here are the most glaring differences (aside from quality).
The BanDai JMs are a little larger than the morphers and have more moving parts.
The transformation for a JM is nearly identical to that of a Taka/Bandai 1/55 valkyrie, while the Convertors/Morphers simply "break-apart" into battroid mode. (Anyone who has seen or hadled one can help me with this description).
JMs can be transformed into all three modes, as where the Convertors/Morphers are only fighter or battroid.
With pics, you will see the difference in quality (which is one of the biggest differences). The JMs are much better in construction and design and poseability - basically better in every way.
Hope this helps!
David