I have used both sanders for extended periods of time. They are very similar and the only noticeable difference is the color. I am almost certain the rest is the same.
Both sanders appear to come out of the same factory. Surfprep is a very new company and Uneeda, who makes Ekasand, has been a family owned business in the United States for over 52 years. I have personally been to Uneeda's facility in New York and met the family and staff who run the company and they are amazing people who have a passion for building and selling only the best products.
Uneeda makes the best sanders and abrasives I have ever used and I highly recommend you purchase the Ekasand. The Idaho Painter.