The M240 is essentially the same size as the M9/M-E: my M-P 240 fit right into the M9 half case. But the controls and screen don't align correctly, so a new half case cut properly for the M240 is needed. The M240 is a tiny smidge heavier than the M9/M-D due to the larger, FAR more robust battery. I hardly noticed the difference. It's also a much more responsive camera, with better high ISO performance, weather sealing, etc etc. The JPEG files on the M240 are much more neutral and usable to my eye ... I disliked the look of the JPEGs on the M9 and simply turned them off entirely.
To me there's simply no comparison. I wouldn't touch another M9/M-E. I'd buy another M240 happily, although I'm now more likely—if I go down the digital M route again—to buy an M10-D. It's doubtful I will because the CL body works better for me overall, and for larger sensor/more pixels I've decided on a different route for the present.
(A CL2 with weather sealing would be nice; whether it's worth the upgrade cost is another question. If they also added the addition of a wired remote release port, I'd put an order in the day they announce it... That's the one thing that's missing on the CL for my use.