To start, the 710 is a 150 Watt marine-band SSB
, and the 718 is a 100 Watt ham-band SSB.
The 710 is legal
for marine-band operation (with the appropriate licenses). It is designed for channelized operation. It can be easily modified (software) for ham operation too (legal with a ham license), but the user interface isn't optimal for that. I have a 710 on my boat, and do occasionally use it on the ham bands.
The 718 is a ham radio
. It may not meet the stringent technical requirements for marine
operation, and while it can be modified for marine-band use it isn't legal
to do so, unless you are in a true emergency
situation. Practically speaking, the radio will probably do fine in marine
operation, but there could be issues. The 718 has a lot more bells and whistles, and is designed for non-channelized operation.
It is easy to mis-configure the 718 unless you know what you're doing. The 710 is more plug-and-play. The 710 is a rock-solid and well-made marine radio. The 718 is probably a great ham radio. Which one is best for you will depend on how you will be using it.