I use 50 w ebos in my nanos. I don't like that they aren't submersible, but they are what is available to me locally, so... that's what I went with. No problems with them so far, other than you have to remove them to clean the salt creep off the dials every now and then.
I have a 250w visi for my 75. I've had it since last winter when the heater that came with the system cooked itself. I have yet to have a problem with it, and had an easier time keeping the tank cooler this summer. Probably because it's thermostat actually works.
For my fw tank, I am using a cheapo TopFin heater, which... oddly enough, has worked surprisingly well given how cheap the thing was. And as cheap as it was, if it dies any time soon, I don't mind replacing the thing.
J.