If the guide’s a good ‘fit’ on the ring and you don’t pedal backwards you shouldn’t have issues, unless you’re doing proper DH stuff I can’t see the need for a ‘full’ guide myself. I’ve never dropped the chain.
The Superstar XCR I have fitted to my hardtail allows my chain to jump off at least once every ride and it annoys the hell out of me! Maybe it’s cos it’s on a hardtail. Maybe it’s cos I’m riding it over some pretty rough terrain too (though it has come off twice on very smooth singletrack), but I’m not back pedalling and it’s definitely setup as well as it can be.
The issue I see with the superstar is the back plate is a little flexy, allowing the cage to be moved by the chain, and the cage is also perhaps 2mm too wide inside for the 10spd chain I’m running. Might be worth modifying by adding a strip or two of plastic inside the cage to narrow it down perhaps, but really it should just work from the factory…
Have just bought a 2nd hand MRP Lopes guide though to try out, figured it’s more likely to keep the chain on as it’s significantly thicker, better designed and has a lower roller too should I choose to keep it on.