The M-802 is the top-of-the
line marine
SSB offered by Icom. It has a removable head which can be located several feet away from the main unit. It also has HF DSC.
The M-700Pro costs about $700 less, but is a very fine and very solid
radio. It does not have a removable head nor does it have DSC.
Both
radios can be used on the ham bands as well as the marine bands, provided you have a proper license. Both
radios can be used with Pactor modems for HF email.
If you absolutely need a
radio with a removable head, you really don't have much choice. The 802 is the radio for you. Ditto if you need/want HF-DSC.
If you don't need either of these features and just want a solid HF radio which will do email as well as
SSB voice, the M700Pro is a good choice.
Bill