Eheim Jaeger is a good brand but I did discover mine won't go past 79 degrees even though the thermostat does read more. So if you ever had to battle ich and turn up the heat, the Eheim won't cut it. Also, they tend to be on the long side so they don't always fit in short/small tanks.
Are you ordering online or buying in a store? If you are ordering online, then I would suggest the Cascade 25w. I have about 5 or 6 of them, plus a 100w for my 20gL and so far they are the best heaters I have. Otherwise, I would go with the Hydor.
Does the white stuff coming from the wound look like it's moving or alive? Is it definitely coming from the wound or from around it?