Most Even-Heating Electric Mattress Pads
Electric Mattress Pad Evenness of Heating (Hot and Cold Spots)
All warming mattress pads heat quite evenly due to their heater wires being held more precisely in their correct heat distribution pattern. Some brands of electric blankets are designed such that their heating wires are free to "float" somewhat inside the blanket. However all brands of mattress covers have their wires held securely in their intended heating pattern.
This is a photo of the bottom side of one brand of mattress pad illustrating their particular method of securing the heating wires in place.
The only major difference between brands of warming pads as far as evenness of heating is found on the Sunbeam heated mattress pads. Many people like the Sunbeam feature of "directing heat where the body needs it" ("Smart Blanket Heating" or "Blanket with a Brain"). However many users complain that this feature actually makes for uneven heating.