I had a Simrad RD68 fixed DSC radio on my rib, also bought a handheld ICOM M1V DSC radio. The Simrad used to give me grief and shortly before I sold my Rib the screen was starting to go and if you check another Forum you will find quite a few other members have had problems with their Simrads RD68's and getting no usefull advice backup from Simrad themselves.
Found the relevant links for you:
Simrad RD68-My Experience
The ICOM M1V I have is excelent, although I do not know what range it has as yet, have been round IOW and still retained coverage althought that is the extent I have relied on it. The battery lasts a long time and it is easy to use.
Hopefully this will be of some use to you. Good luck