So I found some older threads stating the differences between these two models was the better hydros, tires etc. From what I can tell though the current models have the same hydros, same size of tires. The differences I can see easily are the folding rops, better seat, and better engine on the SD. Is there anything else that separates the models? Also changing the topic a bit, what is the depth of the deck on the Fastraks, and how does it compare to say the XOne-I? My yard is fairly thick and often stays wet for extended periods in some spots and I would like a mower that can cope, even if it doesnt give the most beautiful cut, so long as it can get through it.