You can avoid boiling problems by having several smaller (in watts) heaters instead of one bigger one that way if one gets stuck on it won't be able to overheat the tank on its own
i have yet to find a heater i like. i used to be a stealth fanboy, but had a few failures. have a few jagers, one works "sometimes". i do have a aquaclear 50w on my 10g that has been great though.
the best advise i can give you, despite heater manufacturer, is to run multiple smaller heaters with a dedicated temp controller, like the ranco.
i'm all done with glass heaters.. i've had too many break for no apparent reason.
i like the stealth heaters, i bought a bunch of used ones, so i don't really know the brand. but they have been great. the first one finally gave up the ghost a couple weeks ago.
i've been using the ViaAqua titanium heaters for awhile. i like them most of the time but after 3 years of using them about half have quit working. none of them overheated though.. so that is a good thing.
i just bought a heater from petmountain, i forget what brand it is, but it was the only one they had that was 400W. i'm looking forward to putting it in the 210 and taking one of the 250W stealth heaters out.
You've got to squeeze the city by it's gonopodium to scare one up but it's totally worth it. Just watch craigslist and start hoarding them. You'll never regret it. Very few ever die.
Also,
A. Which of the above do you recommend?
B. What is the minimum heater wattage I can get that will heat my tank, and also if it overheats still cannot go past 95 degrees and boil my fish? I have a 40 gallon and a 90 gallon. (I had a tank overheat killing a Jardini and RTCxTSN, so I'm quite traumatized about boiled fish)