Here is my take...
Oddysea is a knock-off brand. For what really good heaters cost, I frankly can see no point in buying anything but the best when it comes to heaters. One malfunction and your tank is dead, and you are going to lose a hell of a lot more than 16.90. Additionally, the Odyssea heater uses stainless steel for it's heater casing, which will eventually erode under saltwater. If a metal case heater is your thing, you should use a titanium cased heater.
You can get two 250w Jager heaters for about $40. That's more than twice the price, but it's still only $23.10 more.
I wouldn't trust any of my aquariums to anything but the best heaters. I also always run two, so if one fails you still have some heat until you fix the broken one.