the fluval e-series is really the cats pajamas for me..although for in sump use, what makes it attractive to me may not be such a big deal in a sump. i originally ran them in my discus tanks, and the color coded digital readout was easy to read across the room (green is good...red or blue will get me off the sofa to see how many degrees off it swung), the plastic cage gave me some sense of security as i didnt have to worry about my fish trying to lay eggs on it, theres a low flow indicator that ensures you put the heater in a high flow area...
but for use in a sump, i can see a lot of those features are kinda moot. i used to be a big fan of ebo jagers, but not really a fan of bi-metal strip controlled heaters (ie non digital) anymore. ive got a few still kicking around, but the writing is on the wall, and their time is coming..