Yes, they are smaller. I don't have a pic to compare, but some measurements may help.
The MX bodies are about 2-3/4" in diameter, MXJ spools are about 1-3/8" wide and MXL's about 1-3/4" wide.
JX bodies are about 3" in diameter and the spools are about 1-1/2" wide.
MX's will get the job done just fine
I also have LX's and use them for 'buts and trolling albies.