I only own one non-submersible heater, and it's definitely more of a pain than the submersible type. I don't like the screw clamp that holds it onto the edge of the tank, and I don't like that I have to unplug it every time I do a water change. Submersible avoids these problems and also gives you more flexibility in heater placement. Finally...the non-fully submersible ones could break just like the submersible ones and expose your fish to loose current just as easily, so there's really no advantage to non-submersible there. If you're worried about breakage, get a shatterproof heater like the Stealth.
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