It's not that units sold at Lowes/HD are different/worse than at dealers, it's that the D___ series are imported and more cheaply-made than the US-made X___ series, and HD/Lowes only carries the D-series. A D-series sold at Home Despot is 100% identical to a D-series sold at a dealer.
Fully aware of the above, the price differential steered me to the D series when I was considering a rider. I had neither the need for features that the X series had, nor the money to pay for one. Yes D-series is more cheaply-made, but it's also correspondingly cheaper. Paying more for higher quality is good to a point, and that point differs according to different people's finances, risk-tolerance, and predilections.