No one rates ease of use but to me it's the most important feature. You could download some Manuels for the units you are interested in and read thru them.
I bought a Horizen 890 a while ago. When I take it out on the Flying Scot, which I usually solo, it's a little too complicated to switch between functions. I can barely let go of the tiller long enough to operate it much less take my eyes off the water. Volume up/down takes several step as does squelch. It's the multi-function keys (Soft keys) that make it complicated. If it exists, I'd like a dial for volume and squelch.
I do like the dual watch and triple watch. You should monitor channel 16 (Actually it's the law) and at least one working channel. I programed mine to scan a group of channels that would cover most my uses - channel 5 for the sailing center, 9,11,13 for bridges and marine traffic, 16, 71,72 for race committee. But if I'm out alone it's the dual scan.
As for the digital calling - it would be useful in RC work to keep communications quiet but all the other radios would have to be synched and that's never going to happen. But maybe you and your buddies could make use of it.
The MMSI is a good feature and I have programed mine. Imagine a medical emergency on the water. Wouldn't you want help to know exactly where you are.
FM radio - a nice touch but not necessary.
GPS, compass, tracking, waypoints ... some use for RC work but not useful for solo sailing. If you have that feature on your radio you should put your marina of launch site in it. In poor visibility you could get home if you don't already have GPS.
