I would go with the rena over the eheim. Reason's being you can do more feedings per day, its heated so your food does not clump with the humidity (though the ehime dose have this as well), it has a power cord so you dont have to stress about the batterys and a photo sensor so you can set it to feed only during the day. No slight to RC but Golds sells them but they are a little more expensive.
http://www.petsmart.com/product/inde...ductId=2752398