Overall: On paper, these stores appear to be identical, offering big discounts on designer labels. While a no-frills store layout is a factor in both, there is a big difference between the quality of the brands and, therefore, the prices.
At Nordstrom Rack, the focus is on more exclusive designer labels, which means it's generally more expensive. At TJ Maxx, there is a wide mix of lesser-known labels, affordable designer brands such as Calvin Klein and Ralph Lauren, and a few "premium" labels scattered in between.
Overall, Nordstrom Rack was the winner. While it is expensive, you do feel that you are shopping for better-quality products.