I may not be qualified to reply in this thread because I have not mowed with either of these machines,
However this spring while shopping for a new mower I did look at both of them.
The Hustler was at a Farm Implement dealer but they sell Hustlers also.
I don't recall the model but it was a 61" deck with a 34 HP Kawasaki and the pump and drive system was the biggest I ever saw man it was heavy built.
When I commented on the pump he said yes it is the same one used in our combines.
Now if it can power a big combine in the field it sure will move that mower.
That may explain why if you watch a video on U Tube of a race between 6 ZTR mowers the Hustler won.
If you are pricing the same size deck and the same engine their should not be $1000.00 difference if anything the Hustler should cost more.
The X-Mark is a great mower but it is sure as hell not worth 1K more.
The Hustler that I looked at was the only one he had at the time and it was more mower and more money than what I wanted or needed but I was very Impressed with it.