Yes, they ARE different. You're talking apples and oranges and...well...footballs.
First, single-sideband (SSB) is a TYPE OF RADIO EMISSION, not a type of radio. Other types of emissions include FM (like the FM radios we're all familiar with), AM (like the AM broadcast radios we're long familiar with), CW (or Morse code), TTY (or data), etc.
What's confusing to many people is that in the marine world, the term "SSB" has come to mean a high-frequency (HF) transceiver type-approved for use in the marine services, and capable of SSB emissions.
In reality, lots of other radio services use SSB emissions. These include the amateur radio service where MOST voice communication on the high frequencies is via SSB, long-distance aircraft service, military and, yes, even Citizens' Band where SOME CB transceivers are capable of SSB emissions within the Citizens Band (27MHz).
So.....SSB is a TYPE OF EMISSION...not a type of radio.
The Cobra radios are basically designed for use on the 27MHz Citizen's Band. They are not designed for use in other radio services or on other bands, to my knowledge.
Modern amateur radios are very sophisticated and can be modified to work on the HF marine bands (i.e., 2, 4, 6, 8, 12, 16, 22 MHz bands), as well as the amateur radio bands. However, it is ILLEGAL to transmit on the marine bands with an amateur radio, except in a bonafide life-threatening emergency.
Marine radios, like the Icom M802 and the Furuno in the link above, are real marine-band HF radios. They are constructed to a higher standard, and meet higher limits of clean signal (spurious emissions) than do amateur radios. There are other differences as well, some of which account for the higher price of these radios.
The aforementioned prices are common, but not necessarily imperative, particularly if you're willing to do a bit of study and get a ham license (note that CW or code proficiency is NO LONGER REQUIRED...you just have to pass a written exam). For some insight into this, please see: http://126.96.36.199/DiscBoard/viewtopic.php?t=2264
Hope this clarifies things a bit.
S/V Born Free