Does anyone know why two companies have such different ratings? Is the Eheim Jager so much better than a Fluval?
They have such different ratings because there is no standard. If all companies were measured against a standard from a testing company, then they'd be comparable.
The price difference is likely based on components used in construction, and to a less extent brand name (or at least it was - typically smaller name products that get recognition for quality and become popular are bought up by larger named companies who squeeze them for all the profit they can get by cutting corners). I'm not certain about Fluval, but I had what I thought was a nice Visitherm heater clink against a tank lightly and the glass shattered into pieces. I've had a number of Jager heaters bang against the tank, but they've got a thicker glass case and have never shattered.
The argument I can see for multiple heaters is that there is a less likely chance that they'll both fail at the same time, in the same way. That is negated though if they are both controlled by the same controller, as it's my impression that the controller/regulator is the part that tends to fail most often.
