Most of the comparisons I see between ZTR and tractors say that ZTR generally has a higher top speed. Ignoring the fact that ZTR's are quicker to line up for the next pass, what makes them inherently faster than a tractor? Comparing same size mower deck and same engine, is it merely how each are geared differently? Seems to me most will recommend mowing at less than 5 mph yet, I see ZTR's advertising a mowing speed of 8+ mph. What makes the cut at that speed better than a tractor cutting at the same speed?