Speedway probably stocks about a dozen and Allied probably has hundreds, thus the price difference. (Speedway might even get theirs from Allied!) Both units appear to have the same specs, so either should do. “They” say the resistors get really hot in use; maybe you should go with a higher wattage unit. Same voltage and current ratings and ohmic values, but higher watt rating to handle/dissipate the heat. And mount it on a heat sink of some kind (hunk of aluminum flat bar) where it will get some air flow. Use heat sink compound, also.