The Tetra or Top Fin or whatever are poop. I have used the Tetra in a pinch, and you couldn't give one to me for free. Hate those things. I wouldn't heat up a cup of coffee with those.
I have used (and still use!) old school Marineland Visi-Therm heaters. I have two running on my 55g that are ten years old. They've were in use for about 3 years and stored improperly the rest of the time. And they're still running like a boss! My other Visi-Therm did spring a leak after storage, but that one was was about used for 5 years more than the others. So, they seem like real work horses. Have good reviews. When they die, I'll probably replace them with the Aqueon Pro below.
I just bought a new Aqueon Pro 100W for my 25g. Has good reviews. Since its encased, it seems like a good choice for larger and/or more active fish. And it looks ninja, really doesn't detract from the vista at all.
I've also heard great things about the Hydor Theo. Though, they're ugly as all get out.
My LFS uses all three of these in their tanks, and has for years. So, to me, that's a concrete endorsement.
I don't know about the higher end models, like Fluval, Eheim, JBJ, etc. Maybe someone else can educate us on those.
As an aside, its interesting how the WPG recommendations have changed. It used to be 3-5 WPG depending on size. Now its how many gallons you have AND how many degrees above room them the water needs to be. The new guidelines make much more sense! YAY for logic!