OK, I just called Jensen Marine and here is the skinny on the MSR2007 and JMS2212:
1. The Jensen MSR2007 came out in 2007 (they also have a 2107 that came out in August of 2008).
2. The MSR2007 head unit is the same size as the JMS2212.
3. The MSR2007 unit only supports 10 models of ipods; the JMS2212 supports all ipods.
4. Both units require a special cable to connect your iPod (someone please let me know if this is true)
5. The MSR2007 does not have a USB port-- This USB port is meant to work with a 4GB jump drive.
6. Both units support SIRIUS Satellite Radio but the MSR2007 only works with the older connections (I am not a user so I am not too sure of the terminology on this)
7. The MSR2007 is 160 watts and the JMS2212 is 200 watts.
8. There might be some issues on "warranty" claims of the MSR2007 since they are so old -- the rep indicated that this is because of internet sales being what they are.
9. Both use RCA plugs for connections to other devices (please confirm if this is true for the JMS212).
From what I can tell the MSR2007 is a nice inexpensive radio:
Here is a link that lists one for $79 (remanufactured).
e-bay List (search for Jensen MSR2007)
I hopes this write-up helps.