I use both. The Ring Free I run with the 100hr maintenance. It's expensive stuff!
The fuel stabilizer and conditioner I run more often, but not every time. Depends on our boat usage. During the summer, gas wasn't in the the boat that long before it all burned up. We plan to boat year round, but obviously our gas is lasting longer now that we're in October so I've been adding in the stabilizer.
I can't comment on the long-term effectiveness in that this is our first year with the boat, but we will hit 200 hours on the engine before November is over. I did some research on Ring-Free and found mostly favorable comments from folks, with most recommending it.
I also picked up a can of Yamaha Yamashield (rust and corrosion prevention spray) that I spray on with the 100hr service.
In addition, I only run ethanol free gas, mostly 87 octane as that's what's most gas stations on the water around me have.